PREDICTORS OF PRESCHOOL PERFORMANCE SKlLLS OF EXTREMELY LOW BmTH WEIGHT CHILDREN

AT THREE YEARS OF AGE

Laurie Margaret Snider

A thesis submitted in confomiity with the requirements for the degree of Doctor o f Philosophy

Graduate Department of Education University of Toronto

Copyright by Laurie Margaret Snider 1 997

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The snidy was undertaken to examine extremely low birth weight (ELBW) preterm three

year olds m order to determine the relationship between perinatal risk variables and preschool

performance. A multivariate risk index congsting of eight risk predictors (birthweight, geaational

age? number of days ventilated, presence of brah lesions, presence of bronchopulmonary

dysplasia, srna11 or average weight for gestational age, gender and socioeconomic aatus) was

designed and seven outcome variables of the Peabody Motor Scales (PDMS) and the Miller

Assessment for Preschoolers (MAP) were exa-ed m a regression analysis. The risk index was

moa accurate in predictmg the MAP Nonverbal Index (which measured memory and visual-

spatial perception) and the MAP Complex Tasks Index ( which measured skiIls combining visual-

spatial perception and motor planning). Gender, Birthweight, Bronchopulmonary Dysplasia and

Brain Lesion entered most fiequently at levels of sipficance mto logistic regression analysis

between the risk index and outcome measures. Comparative analysis of the data indicated that this

population of ELBW preschoolers were performbg one standard deviation below the mean in

gross motor and fine motor s l d s as measured by the Peabody Motor Scales and below the

fortieth percentile on the Miller Assessment for Reschoolers in other domams of preschool

performance. The nsk index successfùlly classined ELBW preschoolers at a rate of 80 percent at

extreme ranges of performance on the MAP Nonverbal index and the Complex Tasks Index.

Lrnplications for use of corrected vs uncorrected age scores for the ELBW population are

discussed as are the relative mengths and weahesses of their skills in preschool performance

domains.

ACKNOWLEDGEMENTS

1 would like to express my gratitude to those who provided me with ongomg support and

encouragement during the completion of this dissertation. I am gratefid for the support of the

OISE scholarship fund which made the initial transition hto academic life less of a financial

concem. In addition, my appreciation to Dr. Hilary Whyte and Dr. Vu@a Frisk of the Hospital

for Sick Children for their guidance during the coilection of the maial data. N o m Himrnel's

assistance with the logistic regression analyses was invaluable and essential to the £inal

development of the work.

1 would like to thank Dr. Kathleen Bloom for acting as extemal examiner for the h a 1 oral

defence of the dissertation. My thanks to the members of my cornmittee: to Dr. Carol Musselman

for her detailed and constructive scmtmy during the thesis preparation; to Dr. Anne Jordan for her

helpful hsights which served to clan@ the work: to Dr. Judy Friedland for acting as the extra

departmental examiner; and to Dr. Tom Humphries, for acting as mtemal examiner and also for

his patient nippon over the ten years that we worked together in clioical research. To Dr. Linda

SiegeL who worked tirelessly with me throughout the project as my çupe~sor, and who

generously shared her expertise m the field of premahinty, 1 extend my deepest gratitude.

My fiend and professional colleague, Joan Ferguson, played an instrumental role m the

successful completion of this project by having faith m me and my work and showing me that she

believed in me during a penod of pahfi.~I transition.

To Julia, my boon companion and inspiration for many years across many miles, 1 extend

my warmest appreciation and &endship. To h i n e , my dear and gentle fiend, who quietly listened

during many late night, long distance cails to Seattle, my profound respect and gratitude.

My lifelong fiends and mentors, Dr. Marian Packham and Jim Packham have shown me m

their steadfast way. what love and loyalty is. Theirs is a mode1 for life well lived and 1 am m their

debt for the b d n e s s which they have shown me over the past three years and throughout my

Me.

1 am thankfiil for the encouragement which 1 r ece~ed fiorn my parents who have aiways

emphasized the importance of education and excellence. I am also gratenil to the mernos, of my

grandfather, Ernea Harold Worden B.A.. MC., who served as an educator and Principal for maoy

years at Weston Coilegiate School in Weston. Ontario. 1 believe that he would have been very

proud of me in the final completion of this academic work.

I extend my heart to Vema Vowles, who has shown me the unconditional and constant

love of a kind and wise woman. My sister, Nancy M e , bas been my cornrade-in- amis during

the Toronto years. 1 don't lmow what 1 wodd ever would have done without her.

FinaDy, to my cornpanion and partner, Richard, my devotion and my joyfùl appreciation

for his strength and cornmitment toward my successfw completion of this work-

TABLE OF CONTENTS

PAGE

CHAPTER I

....................................................................................................... INTRODUCTION 1

CHAPTER II

LITER4TURE REVIEW

........................................................................ 2.1 Introduction 5

........................................................................... 2.2 Bkthweight 5

2.3 Brain Lesion .......................................................................... 8

2.3 1 Intraventricular Haemorrhage .................................. -8

2.3 2 Periventncular Leukomaiacia ................................. 1 4

................................................................... 2.4 Gestationai Age 17

........................................ 2.5 EKects of Rolonged Ventilation 1 8

............................................... 2.6 Bronchopuhonary Dyspla sia 19

.......................................................... 2.7 Socioeconomic Status 20

................................................................................. 2.8 Gender 21

......................................................... 2.9 Methodological Issues -22

2.10 Corrected and Uncorrected Age ......................................... 24

....................................................................... 2.1 1 Risk Indices 26

.......................................... 2.12 School Performance Outcornes 28

....................................................................... 2.1 3 Conclusion -30

.............................................. 2.14 Statement of Hypotheses 3 1

CHAPTER III

METHOD

3.1 Subjects.. ............................................................................. -3 2 -- ............................................................................ 3.2 Measures.. J 3

3.2 1 Peabody Developmental Scales (PDMS).. .............. -33

3.22 Miller Assessrnent for Preschoolers ( MAP). ........... -34

3.23 Risk Index Variables.. .............. .. ........................ .3 8

-9 7 ............................................................................. 3.3 Procedure 39 '* 3.4 Data halysis ....................................................................... 40

CHAPTER IV

RESULTS

............................ 4.1 Data Analysis for Two Nursery Groups -4 1

4.1 1 Means, Standard Deviations, Ranges of Risk

Predictors and Preschool Performance Outcornes

............................................ Between Nursery Groups.. 4 I

4.1 2 Comparison o f Nursery Groups on Risk Predictors. 46

4.13 Comparison of Pre-scbool Performance

Outcornes Between Nursery Groups.. ........................... -46

1.14 Cornpanson of Preschool Perfonnance Outcomes

of Nursery Groups to a Standardized N o m ................. 47

4.2 Data Analysis for Combmed Nurseries ............................ .... 1

4.2 1 Means, Standard Deviations, Ranges of Risk

Predictors and Preschool Performance Outcomes for

...................................................... Combined Nurseries. .5 1

4.22 Total Sample: Comparison of Preschool Performance

.................................. Outcornes to a Standardized N o m 54

4.23 Stepwise Regession Analysis.. ............................... -5 9

4.24 Logistic Regression Analysis. .................................. -67

........................................ 4.25 SensitMty and Spedicity 73

CHAPTER V

DISCUSSION .................................................................................................. 76

CHAPTER VI

CONCLUSION

......................................................... 6.1 ClinicaI Relevance of the Study 82

6.2 Limitations of the Study ................................................................... 83

REFERENCE LIST .................................................................................................... 84

.4 PPENDICES ............................................................................................................. 92

LIST OF TABLES

Table 1

Table 2

Table 3

Table 4

Table 5

Table 7

Table 8

Table 9

Descriptive Statistics for Predictors by Nursery.. ...................... ..42

Descriptive S t atistics for Redictors by Nursery ......................... -43

Descriptive Statïdcs for Peabody Motor Scales for Corrected

....................................... Age (CA) and Uncorrected Age (UA). 44

Descriptive Statistics for Miller Assessment for Preschoolers

for Corrected Age (CA) and Uncorrected Age (UA) by

................................................................................... Nursery.. .45

Coqarison of Peabody Motor Scales for Corrected Age (CA)

and Uncorrected AGE (UA) by Nursery to a Standardized

Nom ........................... .... .................................................. - 4 8

Comparison of Miller Assesment for Preschoolers for

Corrected Age (CA) and Uncorrected AGE (UA) by Nursery

............................................................ to Standardized Nom.. -50

Descriptive Stati~dcs for Redictors - Total Sample ..................... 52

Descriptive Statistics for Redictors - Total Sample ..................... 52

Desc-riptive Statistics for Peabody Motor Scales for

Corrected Age (CA) and Uncorrected Age (UA): Total Sample - 3 3

Table 10

Table 1 1

Table 12

Descriptive Statistics for Miller Assement for

Reschoolers- Total Sample ........................................................... 53

Cornparison of Peabody Motor Scales and Miller Assessment

for Reschoolers to a Standardized N o m for Corrected Age

(CA) and Uncorrected Age (UA): Total Sample.. ......................... -5 8

Summary of Stepwise Regressions: Correlation & Variance

Results for Peabody Scales for Corrected Age (CA) and

................................................................... Uncorrected Age (UA) 6 1

Table 13 Siimman, of Stepwise Regressions: Correlation & Variance Results

on Miller Assessment for Preschoolers for Corrected (CA) and

Uncorreaed Age (UA) for Foundations, Coordination and

....................................................................... Nonverbal Indices.. .62

Table 14 S v of Stepwise Regresàons: Correlation & Variance Results

for Miller Assessment for Preschoolers for Corrected Age (CA) for

Verbai, Complex Tasks and Total Score hdices ............................ 63

Table 15 Surnrnary of the Results of Stepwise Regression: Correlation and

Variance for Predictor Variables on Peabody Motor

Scales for Corrected Age Scores (CA) and Uncorrected Age

............. .......*..*...*.................*..*..*...*..*............ Scores (UA) ..... ..64

Table 16 Summary of the Results of Stepwise Regression: Correlation and

Variance for Predict or Variables on Miller

Assessment for Reschoolers for Corrected Age Scores (CA) and

Uncorrected Age Scores (UA) on Foundations, Coordination and

Nonverbal Indices.. ....................................................................... .6 5

Table 17

Table 18

S- of the Results of Stepwise Regression: Correlation and

Variance for Predictor Variables on Miller

Assessment for Preschoolers for Corrected Age Scores (CA)

on Verbal, Complex Tasks and Total Score Indices ....................... 66

Peabody Motor Scales: Summary of Results of Logistic Regression

for Redictors Entering the Equation using Corrected Age (CA) and

.................................................... Uncorrected Age (UA) Scores.. .70

Table 19 Peabody Mot or Scales Logistic Regression: Percentage Rate of

Correct Redicted Classification Usbg Corrected Age (CA) Scores

and Uncorrected Age (UA) Scores .............................................. ..70

Table 30

Table 2 1

Table 22

Table 23

Miller Assessment for Preschoolers: Summary

of Results of Logistic Regression for Redictors Entering Equation

Using Corrected Age (CA) and Uncorrected Age (UA)

........................................................................................... Scores -7 1

Miller Assessment for Preschoolers Logistic Regression: Percentage

Rate of Correct Predicted Classification Using Corrected Age (CA)

and Uncorrected Age (UA) Scores ................................................ 7 1

Miller Assessment for Preschoolers: Summary of

Results of Logistic Regression for Redictors Entering the Equation

............................................. Using Corrected Age (CA) Scores ..72

m e r Assessment for Preschoolers Logistic Regression:

Percentage Rate of Correct Redicted Classification Ushg Corrected

Age (CA) Scores.. .......................................................................... -72

Table 24 SenntMty and Speciiicity of Risk index for Outcornes Correctly

Classilied >79% Using Corrected Age

(CA) Scores and Uncorrected Age (UA) Scores. ............................ 75

LIST OF FIGURES

Figure l

Figure 2

Figure 3

Comparison of Means of Peabody Motor Scales:

Gross Motor and Fme Motor Scales to Standardized

.................................................................. N o m ............... ,.. 5 5

Comparison of Means of MiUer Assesmient for

Preschoolers to the 50 % de:

Foundations, Coordination and Nonverbal Indices.. ................... -5 6

C omp arison o f Means of Miller Assessrnent for

Preschoolers to the 50 % ile:

Verbal Complex Tasks and Total Score Indices ......................... 57

LBT OF APPENDICES

Appendix A: Predictors Correlation Matrix.. ............................................................ -93

Appendk B: Predictors / Outcome Variables Using Corrected Age (CA) Scores

Correlation Matrix.. .............................................................................. -94

Appendix C: Predictors / Outcome Variables Using Uncorrected Age (UA) Scores

Correlation Matrix ............................................................................... -95

Appendix D: Outcome Variables Using Corrected Age (CA) Scores Correlation

Matrix.. ................................................................................................ -96

Appendix E: Calculation for Sensitivity and Specificity Values for Logistic Regression

Outcomes Correctly Classified at a Rate of Greater Than 80%: MAP

Nonverbal (CA).. ................................................................................ -97

Appendix F: Calculation for Sensitivity and Specificity Values for Logistic Regression

Outcomes Correctly Classified at a Rate of Greater Than 80%: MAP

Nonverbal ( UA). ................................................................................. -98

Appendix G: Calculation for Sensitivity and Specificity Values for Logistic Regression

Outcomes Correctly Classified at a Rate of Greater Than 80%: MAP

Complex Tasks (CA).. ......................................................................... ..99

Appendix H: Glossary.. .............................................................................................. LOO

Appendix 1: Frequency Distniutions for MAP Nonverbal Index Scores

(corrected age) ..................................................................................... 103

Appendix J: Frequency Distn%utions for MAP Nonverbal Index Scores

(uncorrected age) ................................................................................ 104

Appendiv K: Frequency Distniutions for MAP Complex Tasks Index Scores

.................................................................................... (corrected age) 105

Chapter 1

The developmental outcome of mfants bom prematurely has been a subject of

ueat interea to investigators (e.g., Frisk & Wbyte, 1994; Hack Tayley, Klem, Eiben. C

Schatscheider & Merctni-Munich, 1994; Mazer, Piper & Ramsay. 1988; Piper, Darrah.

Bryne, & Watt, 1990; Scon & Spiker, 1989; Siegel 198 1, 1982, 1983, 1988) because

the preterm mfant is identified at birth a s bemg at risk for a constellation of dZEculties

includmg major neurological sequelae, minor neurological sequelae, mental retardation.

learning disabilities and sensory handicaps. As complex technological advances are made

in neonatal Mie support systems and more mfants of extremeiy low birthweight (ELB W:

birthweight < 1000 grams) surcive, the questions continue to present themselves: How

does this group of even lower birthweight babies fare in long term developmental

outcomes? What are the similarities and differences between this Iowea group and

previously snidied groups? Has the medical care using the new technology improved

the quality of Me for these individuals? What are the risk factors which significantly

affect the developmental outcomes of this group? The challenge has been to identlfy the

critical risk factors which may act aione or together in order to detennine what the long

term outcome of groups of &ors with increasingly low birthweight will be.

The long-term outcome of children bom prematurely is determîned by a number

of variables which a a either done or m combination. These variables mclude the presence

7 -

of periventricular bram lesions which may develop during the perinatal period and other

medical complications which range m their severity and number (e-g., Lewis &

Bendersky, 1989). Fuller, Guthrie and Ahord ( 1983) proposed a neuropathological

rationale for the presence of minor and moderate neurological deficits m the premature

infant population. in the study, autopsies of 16 mtànts boni premanirely who had died

withm the ikst month of Me, showed brain damage m the cortical and basal areas of the

bram. The interruption of neural pathways caused by this brain damage, or brain lesion,

was niggested to be the basis for later presentation of neurological deficits which would

impair early leaming and motor skills. Low, Galbraith, Muir, Broekhaven, Wilkuison and

Karchman ( 1985) found that poor developmentd outcomes of premature inFants were

associated with the medical complications of fetal hypoxia and respiratory distress in the

perinatal period. The authors proposed that these were the biological mechanisms

associated with poor oxygenation of the brain which were related to brain lesions and

subsequent aeurological deficits. Socioeconornic aatus has been documented as a nsk

factor in low birth weight ( e-g., Siegel, 1982) and male gender has also been presented as

a nsk factor in developmentd outcomes ( e.g., Gold & Huebner, 1970).

Inrprovements in the management and care of the extremely low birthweight

infint have led to lower rates of rnortality and a reduction in the severity of the morbidity

traditionally associated wah the preterm population. However, as the incidence of major

3

neurological sequelae niminizhes in the ELBW group, the relationship between exishg

moderate and minor impairments and pretem performance of the complex tasks

associated with early learning and motor skiUs has raised concem (Aylward, Meiffer.

Wright & Verhula, 1989). The t e m 'binor mipairment" may be misleadmg, giveri the

impact which the disorganized behaviours *lied by the term have on a child's

functional ability. ûther authors (AmieCTison & Stewart, 1989) have suggened that the

minor risk group mcludes children who go on to develop subtle motor difnculties which

interfere with the acquisition of fine motor skiUs and early leaniing. Although these

difficdties are not ''major" compared to severe cerebral palsy, they are nonetheless

signincant in the life of a child who is expected to function and leam within a non-

disabled peer group The relationship of these minor impairments to the leamhg and

motor slcills of the neurolopically mtact survivors of the ELBW group as they approach

school age is of mterest m temis of early identification for potential difficulty in

performance in functional dornams such as school and daity living routines. Other midies

have documented school age outcomes (Hack et al., 1994), but reports on the preschool

performance. that is, at the ages of 3 to 4 years of age, of the ELBW population are

few.

The present study differs fkom previously published works in the size of the

neurologically intact ELBW sample available for observation. The accuracy of the data

4

on sonic locaiization of haemorrhagic and ischaemic lesions reflects the improvement m

curent technology over the resources available at the time of previous -dies. Ahhough

another study has assessed a similar population at preschool age (Crowe. Deitz, B e ~ e t t .

& TeKoIae, 1988), their sample size (n=32) limited the number of variables the

investigators were able to study, and ody renilts on motor ski11 performance were

presented.

The present study examined nonverbal, verbal and complex task as well as

motor domains of preschool performance. It was possible to use a muhivariate anaiysis

because of the relatively large sample, which permitted examination of the separate

effects of these variables on outcornes, m this study of preschool performance skills.

Statement of the Research Problem

This research was designed to mvestigate the relationship between the risk

factors of birthweight (BW), gestational age (GA), weight for gestational age

(AGNSGA), number of days ventilated during hospitalization (# days), presence or

absence of brain lesions (intraventricular haemorrhage [NHl and periventricular

leukomalacia PVL]), presence or absence of bronchopulmonary dysplasia (BPD),

gender, and matemal education on preschool performance skills in a population of three

years olds who were bom premature with extremely low birth weight (ELBW), that is,

at or below 1000 grams, and no medical diagnosis of cerebral palsy, blindness, deafhess

or severe cognitive delay.

Chapter CI

LITERATURE REVIE W

2.1 Introduction

The fiterature on the risk factors associated with reduced developmental

outcomes of pretem &ors is extensive, however, recent idionnation on the ELBW

eroup is less weU developed. The literature on the risk variables mvestigated wîU be C

reviewed, foilowed by a review of methodological issues associated with the study of

developmental outcomes in prematurity. Finally, the studies of preschool and school

outcomes will be reviewed.

2.2 Birthweight

As medical technology and the quality of neonatal intensive care have

improved, increashg numbers of infants of extremely low birthweight are sumivbg the

perinatal course of extreme prematurity. W e very low birth weight (VLB W) is defined

as 1500 grams or less. extremely low birthweight (ELBW) is dehed as a birthweight of

1000 gram or less (Hack & Fanaroe 1989). The ELBW category represents premature

infants who are extremely biologicdy immature and medicaIiy fiagie. Medical care for

the ELBW infant is given over many months m a neonatal intensive care unit. Reviously,

most of these infants died or were extremely neurologicaliy damaged. However, a

6

reduced chance of death or the mcidence of major neurological sequelae in the ELBW

population has been reported m recent years (Cooke, 1993; Lee & Barran. 1994).

Perlman, Clark, Hao, Pandidt, Whyte, Chipman & Lieu ( 1995) analysed the rate of death

and the incidence of major impairment m 287 mfants bom between 1980 - 1989 weighmg

800 gram or less and foliowed to two years of age. Over this period, the authors noted

an mcreasing refend rate of ELBW mfants in which the death rate did not rise

sigdïcantly (4 < .12), and the rate of major impairment feu (p < .002). The latter

largely resulted fiom the reduced incidence of blindness which was attributed to better

neonatal intensive care procedures, such as physiological monitoring. Wojtulewicz

Alam, Brasher, Whyte, Long, Newman and Perlman ( 1993) also noted ùnproved

outcomes in babies of 500-750 grams over two periods ( 1980- 1983 and 1984- 1987).

The nirvival rate increased fiom 32% to 54% ( p<.002) and the rate of major

impairment decreased fiom 4 1 to 14% (p<.005). In addition, the incidence of children

who tested as having no impairment on the Bayley Scales of Mant Development (Bayley,

1969) at two years of age increased clinically, although not to the point of statistical

àgrilficance. This effect was confined to the 500 - 750 gram birthweight group and was

thought to reflect improvement in neonatal intensive care practices. The other birthweight

groups' survival rates and rate of major impairment remained the same.

Jarvenpaa, Vlrtanen and Pohjavuori ( 199 1 ) reported an increase in the number of

ELBW h e births and a concurrent increase in the number of sunhving ELBW infants

over a six year period. There was also a decrease m the fiequency of brain lesion among

the &ors, the fiequency of major disability decreased fiom 28% to 8% and there was

7

an mcrease in the number of normal neurological examinations at two years of age.

Birthweight was one of the variables that had the greatest significance on neurological

outcome at one year of age.

Birthweight has been found to be an important factor m determinhg

developmental outcome aatus in other studies. Bennett. Robmson, and SeUs ( 1982)

found that low birthweight was a more significant predictor of poor developmental

outcome on the Bayley Scales of Infant Development than eitber respiratory aatus or

gestational age. Mazer, Piper, and Ramsay ( 1988) found that birthweight was one of the

important factors which affected the results of developmental testing. These authors

divided a cohort of 78 VLB W mLuits into three birth weight categories: ~ 7 5 0 g,

750- 1000 g, 100 1- 1500 g. They then followed the children prospectively to 36 months

of age. Developmental testing was done at 6, 12 and 24 months corrected age and at 36

months of uncorrected age on the five SM areas of the GrifEths Mental Scales of

Development ( m s , 1954). The results showed poorer performance in a l skilI areas

between the 100 1g - 1500g birthweight group and the 750g - lOOOg birthweight group.

The < 750g birthweight group showed signiticantly poorer performance than the other

birth weight groups on four of the £ive sW1 areas (locomotor, personaUsocial

hearinglspeech, eye hand coordination) This lowest birthweight group's renilts in the

sfth skill area (performance) were clinically lower than the middle birthweight group

and significantly lower than the highest birthweight group. The results thus showed a

stratification of the scores fiom each birthweight group mto three distmct levels, with

diminishing performance according to decreasing birthweight across ail domains.

8

Hack Tayler, K l e m Eiben, Schatschneider and Mercuri-Minich ( 1994) studied a

regional cohort of 68 ELBW school age children with birthweights under 750 gram and

found infenor performance in psychomotor skius school performance and cognitive skills

compared with two matched groups of children with higher birthweights, one group with

birth weights of 750 to 1499 g r a m and the other group bom at term with normal

birthweights. The results supported the previous study (Mazer et al., 1988) m that

decreasing performance based on decreasing birthweight was observed.

in nimmary, previous stuclies found that birthweight is a good predictor of

subsequent developmental status. While the degree of impairment increases with

decreasing birthweight. more mfants of ELBW are nirvivmg without major impairment.

2.3 Brain Lesion

2.3 1 Intraventricular Haemorrhaee

The incidence of brain lesion in the ELBW population was reported to be 25-

40% (Volpe, 1990). Since ultrasound technology has become more accessible to

neonatologists, making visualization of the brain structures possible, the presence of

lesions in the preterm brain has been descnïed increasingly in the recent literature.

Hellman and Vanucci ( 1982) found that the incidence of mtraventricular haemorrhage

(NH) is related to the neuroanatomy of the preterm bram. Ninety percent of IVH

occurred in the subependymal germinal matrix mferior to the lateral ventricles of the

brain, an area which is highly vascularized at 24-32 weeks of gestational age. As a

result. there is injury to the corticospinal fibres which pass through the subependymal

9

area fiom the cortex to nipply rhe motor system Sufficient damage to the brain tissue

in this periventricdar region c m also interrupt the Msual and motor pathways which

traverse this area. This central nervous system damage can result in cerebral palçy, one of

the major neurological sequelae assuciated with preterm bkth (Pape & Wigglesworth.

1979). The localization of the brah lesion will affect the brain structures within the area

of damage and subsequently may be related to difliculty in the abilities controIled by that

area of the brain (Kertesz, 1983). In many cases, the degree of brain damage has been

fomd to directly related to the degree of inipairrnent (Krishnamoorthy, Kuban, Leviton.

Brown, Sullivan. & ABed (1989). Therefore. a minor degree of damage can lead to

minor impairments of the nervous system

Hellman and Vanucci ( 1 982) suggested that WEI occurs when preterm infants

become hypoxic due to poor ventilation, which causes difficulties with autoregulation of

cerebral blood flow. The unregulated higher pressure of arterial blood flow through the

preterm brain exposes the vasculanue to higher blood pressure which is not tolerated by

the fragile, immature capillaries which rupture causing bleeding in the germinal matri.. of

the subependymal areas of the lateral ventricles of the brain (Wigglesworth & Pape.

1978). Mechanical ventilation procedures used in the neonatal mtensive care unit

(NICU) may also contribute to changes in blood pressure and artenal hypertension which

cause haemorrhagic lesions (Heilman & Vanucci, 1982).

Until the advent of diagnostic ultrasound imaging of the brain, diagnoçis of

haemorrhagic and non-haemonhagic brain lesions was limited to the detection of clinical

signs of iVH or computerized tomography (CT) scan. Clinical signs of ll4-I included

10

decreased muscle tone and movement, seizures, abnormal eye movernents, a droppmg

haematocrit, a bulging anterior fontanelle, or overall clinicai detenoration. Reliance on

clinicai signs causes the incidence of M3 to be highly underrated, particdarly in

subacute cases (eg. Crowe, Deitz, Bennett & TeKolste, 1988). Rior to the availability

of CT scans, rnuch of the information on IVH was obtained fiom autopsies on infants

who had not &ed. CT scans p e d s computerized imaging of the brain, but is not

ideal for the fiagile neonate since the mfant is exposed to radiation during the procedure.

Cntrasound technology was substituted for CT scan as a noninvasive way to image the

antenor portions of the living preterm brain using the anterior fontanelle as an acoustic

window. This technology depends on the fact that sound waves echo differentiaily

through various brah tissue densities. The echoes can be visualized, thus enabling

physicians to idente and quanw the extent of brain tissue damage caused by

haemorrhagic brain lesions (Sostek Smith. Katz & Grant. 1987).

Ushg ultrasound technology, a grading syaem to quant* the extent of brain

damage was developed by Papille, Burstem and Burnein ( 1978). ui a grade I iVH, the

haemorrhage remains contamed in the subependymal tissue. A grade II Mi occws when

the haemorrhage ruptures mto the lateral ventricles. Ln a Grade ïII IYH, the ventncles of

the brain are edarged with blood and subsequently put pressure on brain tissue. Grade

N haernorrhage occurs when the pressure of the blood within the ventricle forces blood

back into the brain tissue.

Findùigs indicate an association between brah lesion and developmental di£Eculty.

Krishnamoorthy et al. ( 1989) reported that the ventridar enlargement associated with a

Grade III haemorrhage represented an increased likelihood of spastic cerebral palsy.

Volpe ( 1990) found that 5 to 15 percent of infants with brain letion developed cerebral

palsy and an additional 25-50 percent had developmental disabilities or school failure.

However, Sostek, Smith. Katz and Grant ( 1987), wMe h d m g an mcreased incidence of

developmental difliculties related to TVH in a group of 1 13 pretenn infants bom at < 1750

grams, discovered that over 5 0% of the severe nrtI group was functioning within normal

limits on the Bayley Scales of Infant Development at two years of uncorrected age

(Bayley, 1969). A pilot m d y of the sample at kindergarten age indicated that, aIthough

minor neurological irnpairments were related to the presence and severity of WH, the

severity of brain lesion at birth failed to predict developmental performance at two years

of age. The authors concluded that lVH had Limited value as a predictor of risk status

over tirne.

Stewart, Reynolds, Hope, Hamilton, Baudin, de L. Costello, Bradford. and

Wyatt ( 1987) studied a group of 342 VLBW and ELBW preterm infants bom before

33 weeks gestational age. They reported on the relationship between the ultrasound

appearance of the brain and major and minor central nervous dysfunction. Routine

ultrasound scans were performed several times m the first week of life and then on a

weekly basis until discharge f?om the nursery. The mfants were fobowed every three

months for one year afker discharge and screened developmentaily ushg the

Developmental Screening hventory (Knobloch, Pasmanick, & Sherard, 1966),

neurological, ophthalmological and audiological clinical test S. The Grifiths Ment al

Scales of Development (GrifEths, 1954) were administered at 12 or 18 rnonths.

12

Corrected age scores were used to mterpret the results of testmg. On the ba i s of these

tests, the children were identified as having major (cerebral palsy, aided hearing loss.

mental retardation [Griffiths Mental Scale <70]) and minor (subtle abnormalities of tone.

reflexes, ventricule-peritoneal shunts for hydrocephalus) neurodevelopmentd

impairments. Logistic regression analysis mdicated that VLB W infants with

uncomplicated haemorrhages (grade 1 and II NH) did not have a higher probability of

major or minor diûiiculties than those with normal scans. However. for ELBW mfants

with uncomplicated haemorrhages, there was a greater probability of minor diûicdties.

Further analysis investigated the effects of lesion severity wÏthin this group. Seven

percent of the sample fell into a high risk group showhg hydrocephalus and grade TV

iVH; there was a 58 percent probabihty of major disability. Thirteen percent of the

children were classified as being at intermediate risk (Grade KI), and these had a 43

percent chance of major disability. Eighty percent of the sample (Grade 1 and Grade II)

were assigned to the low risk group on the basis of showing subtle abnormalities of

muscle tone and reflexes which interfered o d y minimaUy with normal hc t i on . Within

this group, only 1 1% had a major disabihty. Thus, the severity of haemorrhage was

related inversely to developmental skilIs and the children in the minor nsk group were

wilikely to develop serious motor impahents.

The categories eaablished by Stewart et al. ( 1987) have been used to make

medical decisions about how long to pursue the care of low birthweight. il1 mfants.

However, there were some limitations to the study. Children whose scans were deemed

normal may weiI have had meported minor ischaemic changes. The authors

13

acknowledged that refinements in ultrasonic imaging, which had occurred since the

inception of the mdy, made the identification of more subtle damage possible. There

was also a tendency on the part of the authors to mmimiie the day to day impact of

9 m h ~ r 7 ' impairments on the day to day Mie of an individual child and his caregivers.

Bozynski Nelsoe Rosati-Skertich, Genaze, O'Donneil, and Naughton ( 1984)

suggested that evidence of IVH. as seen by dilation of the lateral venticles of the brain

which did not regress by the time gestational age for the expected term was reached

should be interpreted as a risk mdicator for compromised developmental outcome.

Children's performance on motor, perceptual, language and personality outcornes at 4. 8.

12. 18. and 24 months of corrected age was poorer in the veiy low bUthweight

popularion (n = 75; birthweight cl200 grams) when the presence of IVH was considered.

Lowe and Papille ( 1990) supported this position aatmg that mild NH compromised

overali performance and that VLBW infants with mild Mi were at nsk for learning

ditficulties. This natement was based on the resuits of a study which followed 38 VLBW

(-4 50 1 gram) dMded into two groups; one group with Grade 1 and II IVH subjects

and the second group with subjects without evidence of brain lesion who were found to

be neurologically and developmentally normal between ages 12 months to 24 months

corrected age. When matched for age and other dernographie variables with a group of

full tenn age peers and compared at age fïve and six years, the first and second groups

scored significantly lower than the third group on outcome measures of cognitive

performance and early reading skills. The fira group of subjects with mild NH also

scored sigdicantly lower than the second group on the outcorne measures.

14

Few shidies have examined the motor performance of the preschool aged ELBW

population who do not present with major disability. Crowe et aL ( 1988) studied a d

sample (n = 32) of ELBW four and a halfyear olds. Identincation of IVH had been

established by ciinical observation only, so that evidence of sub-acute haemorrhage was

not available. Using the Peabody Developrnental Motor Scales (Folio & Dubose, 1974),

the subjects were found to have significantly lower gross and fine motor skills than

published n o m for their chronological age. The subjects who presented with clsiicaUy

symptomatic IVH demonstrated an inferior motor performance withm the sample.

This review of the literature identified some snidies which reported clear

evidence that M-I is associated with poor developmental outcomes. However, not

every study supports this conclusion. The association betweai IVH and subtle

abnormalities in outcome has not been investigated. A similar pattern was seen in the

iiterature which descnied the outcomes associated with periventricular leukornalacia.

2.32 Periventricular Leukomalacia

Periventricular leukomalacia (PVL), a non-haemorrhagic brain lesion. has a

different etiology h m IMI. It is descnied as an ischaemic lesion of the periventricular

white matter. PVL is caused by necrosis of the brain tissue in the periventricular area

which has been destroyed by the blood fiom the cranial haemorrhages. When large areas

of the brain become necrotic, cystic periventricular structures h o w n as cavitary PVL are

formed. PVL is mdicative of extensive anoxic-ischaemic damage to the brain

(Wigglesworth & Pape, 1978). It may appear as a secondary complication of iVi3 but is

also seen in infants who had never suffered either an IVH or respiratory diaress

15

syndrome. Infants with PVL who showed no evidence of IVH had had severe recurrent

apneas (Wigglesworth & Pape, 1978), aithough the etiology for PVL m the absence of

IVH is not clearly established ( Als Lawhom, Brown, Gibes, Du@, McAnulty. &

Blicknian, 1986).

Bozynsk Nelson, Matalon, Genaze. Rosati- Skertich, Naughton and Meier

( 1985) studied the effects of PVL in a group of 1 O0 preterms bom at less than 1200

grams birthweight. These authors found that the majority of srnail early PVL lesions were

transient and had resolved beyond six months of pomatal age. The large ischaemic

lesions showed a higher Iikelihood of becoming cyaic periventricular structures formed

by cavitary necrosis. F i e of the infants m this sarnple showed cavitary PVL. AU of the

fÏve children developed cerebral palsy by 24 months of age. Bozynski et al's ( 1985)

results documented that the presence of iVH and cystic PVL predicted poor

neurological outcome. especially for cerebral palsy. The relationship between the

presence of mild PVL and neurodevelopmental sequelae was less clearly seen.

Bennett, Sihrer, Leung and Mack ( 1990) çuggested that the mild PVL hdiigs

should be more accurately descnied as periventricular echodensities. The authors graded

the ultrasound hdings of PVL for 48 very low birth weight preterm infants. The

grading system ranged from zero to three, with O representbg no findings and 3

representing the formation of cysts. The infants in the sample were followed to a mean

corrected age of 18 months and assessed ushg a medical neurological examination and

the Bayley Scales of Infant Development (Bayley, 1969). The infants were classified into

three groups on the basis of the outcome meanires: normal having minor abnonnalities

16

or having major abnormalities. Fifty percent of the sample were normal 27.1 % had

minor abnormaiities and 22.9% had major abnormalaies. The poorest developmental

outcomes were found m the children who had Grade 3 PVL mdicating c y d c formation.

However, there were no cleariy dehed trends for poorer developmental outcome with

mcreasing severity of periventricular echodensities as not ail the subjects with cystic PVL

developed cerebral palsy. In fact. 40 % of this goup had a normal neurodevelopmental

exam at eighteen months. The findmgs for severity of WEI, on the other han& showed

more severe ditFcuities with increasing severity of haemorrhage. Severe Mi (grade IU

or IV) was reponed as a better predictor of neurodevelopmental performance than

periventricular leukodacia. However, the use of corrected age scores to class@ the

sample into groups on the basis of performance on the Bayley Scales at 18 months of

corrected age to predict developmental outcome should be questioned as Siegel ( 1983)

found. that afier 12 months, uncorrected age scores were more highly correlated with

later outcomes. In view of the vanability m outcomes, Bennett et al. ( 1990) cautioned

against using the presence of PVL as a clear indicator of fùture developmental

diEïculties.

In summary, although the detection of PVL by ultrasound may be associated with

developmental compromise in many cases, a broad range of outcomes ranging fiom

major to minor to normal neurological function has been associated with the presence of

this risk factor.

17

2.4 Gestationai Age

Whyte, Fitzharding, Shennan, L e n n o ~ Smith and Lacy ( 1993) reported on the

monality and morbidity of babies born between 23-26 weeks gestational age. The study

was conducted among three hosplals with specialized perinatal and neonatal intensive

care units. with a total catchment of 60,000 annual deliveries. Of these, 568 infants of

23-26 weeks gestational age were born between July 1982 and July 1987. There was a

39 ?h overall mortality rate, which was inversely proportional to gestational age. Survival

rate at 23 weeks was 11% and at 26 weeks was 50%. A decrease in both mortality and

morbidity after 25 completed weeks of gestation was observed.

Yu. Bajuk Or@ Aabury ( 1985), reporthg on the viability of infants born at

24-26 weeks of age. found an overall survival rate of 44%. with 36% of babies born

a t 24 weeks, 32% of those born at 25 weeks and 57% of children born at 26 weeks

surviving. When re-assessed at two years of age, 67% of the children boni at 24-25

weeks did not demonstrate a sigidïcant functional disability. Of the children born at 26

weeks, 80% were fkee fiom sigaificant functional disability. Forslund and Bjere ( 1989)

proposed that preterm children with gestational ages of less than 35 weeks may score

within the normal range when compared to full term age peers, while functioning in a

lower "borderline-normal" range than their peers in fine motor and visual motor s M I

areas. In a study which compared 44 mfants born before 35 weeks of gestational age

with 25 f'ull-term infants at four years of age, the authors identified a profile of minor

neurological signs which revealed signficant clifferences in the abüities to execute fine

motor and visual motor tasks in the preterm group.

In summary, children of low gestational age are çurvivmg in greater numbers

without major functional disab*. There is some evidence to suggest that minor

irnpairments may have an impact on functional abilities in this group.

2.5 Effects of Rolonged Ventilation

The effects of the prolonged ventilation penod required to support the immature

respiratory system of the preterm mfants have been found to be related to poor

developmental outcome. Bozynsk~, Nelson, Matalon, U'Donnell, Naughton, Ushanalini

Meier and Ploughman (1987) foiiowed a group of 159 VLBW ( 4 2 0 0 g) mfants who

were classified in ternis of the presence or absence of IMI and the length of mechanical

ventilation. The resdts on the Bayley Scales of Infmt Deveiopment (Bayley, 1969) at 4,

8. 12 and 18 months showed no effect for IMI. The group with prolonged mechanical

ventilation showed &culties at each age teaed. Rothberg, Maisels, Bagnato, Murphy.

m o r d and McKinley ( 1983) attributed the poor outcome of 25 ELBW mfants who

were ventilated for long periods to factors such as sepsis. maremal disease,

complications during deiivery, and other morbidity factors present m such children

rather than the actual intervention of ventilation itself. Infants were assessed ushg the

Bayley Scales at 20 to 26 months of corrected age and the GeseU Developmental

Schedule was used at 27 to 7 1 months of corrected age. Significantly greater numbers of

the ventilated infants scored m the severely handicapped range. Significantly greater

numbers of nonventilated infants scored m the normal range of the outcome measures.

These midies bdicated that, although prolonged ventilation was associated adversely

19

with poor developmental outcomes. it was diflïcult to establish whether the intervention

of ventilation was damaging in tseK or whether the mfaats requiring ventilation were

more medically fiagile and therefore more likely to do less well developmentdy over

time.

2.6 Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD), lung tissue damage fkom high oxygen

levels and pressures during respirator therapy, is one of the complications of prolonged

ventilation which has been consistently related to developmental delay (Landry,

Chapieski, Fletcher, & Denson, 1988; Northway, 1979). Children with BPD suffer fiom

poor nutrition during the neonatal course of theû respiratory disease (Frank & Sosenk.

1988; Wilson, McClure, Halliday, Reid & Dodge, 199 1 ), repeated chea infection in the

ka year of life (Tamrnela, 1992) and more neurological sequelae than children without

the disease (Hakulinen, Heinonen. Jokela & Kiekara, 1988). Goldson ( 1983 ) studied a

cohort (n= 17) of VLB W mfants (< 1 100 gram) with severe BPD and a VLBW control

group matched for birthweight and gestational age. Results on the Bayley Scales at two

years of uncorrected age found significant clifferences on mean mental scores. Mean

motor scores were lower but were not significantly Werent. The author stated that BPD

should be seen as a rnarker for subsequent neurological problems.

Landry, Chapieski, Fletcher, and Denson ( 1988) tested a goup of 78 infants

weighing < 1600 gram ushg the Bayley Scales at birth at 6, 1 2, 24 and 36 months of

uncorrected age. The subjeas were grouped according to severity of medical risk for

TVH and BPD. The study found that preterm infants who do not develop IVH or BPD m

20

infancy have a greater Wreliiood of good developmental outcome.

To summarize, bronchopulmonary dysplasia has been found to be consiaently

related to poor developmental outcomes.

2.7 Socioeconornic Status

Teberg, Semlage, Hodgeman, King and AquilBie ( 1989) reported that women of

lower socioeconomic status tended to have an mcreased Nk of low birth weight

pregnancies. The mcreased risks were associated with hypertension and a hiaory of

infection during pregnancy. The authors characterized these clinical outcomes into two

components: demographic (race, d a 1 status, lack of prenatal care) and Mestyle

(alcohol and substance abuse).

In an Australian midy. Lumley. Correy, Newman and Curran ( 1985) found that

the social class factor in low birth weight during the years 1975- 1983 was restricted to

infants in the 1500g - 2500g range, with a minimal increase in the incidence of < 1500g

pregnancies in famiiies of unskilled or unemployed workers. These authors reported that

the incidence of ELBW was consistently distnbuted across the socioeconomic strata.

These hdings suggeaed that ELBW birth may not be as strongly related to SES as

other categories of low weight births.

Forslund and Bjere ( 1989) found that tests results (for preterms bom before 3 5

weeks of gestation) on the GdEths Scales (GifEths, 1954) were correlated with

socioeconomic aatus and parental education. Lewis and Bendersky ( 1989) reported that

SES predicted language ability as well as information processing ability. Siegel (1982)

2 1

reported that IQ scores and language scores of 53 VLBW and 5 1 fd tenn mfants were

sigruficantly correlated with SES. Lowe and Papille (1990) found that SES, as estimated

by mothex's level of education, was a primary predictor of acadernic grade levels for

preterm infànts. Ross, Lipper and Auld (1985) found that SES was less predictive of

preschool outcornes in ELBW than the results of the medical neurological examination at

one year of age. Although SES did predict cognitive ab* at three years of age. it did

not predict neurological aatus or sensokmotor skills at that age.

In nimmary. SES has been found to be correlated with pretem developmental

outcornes. However. some evidence mdicates that the incidence of ELBW may not be as

strongly associated with SES as is the incidence of other birth weight groups and that

SES may not correlate with the neurological status or sensory - motor skills of ELBW

children at preschool age.

2.8 Gender

Numerous authors have found that boys have a greater risk for learning disability

( Gold & Huebner, 1 970). developmental disabhy such as epilepsy (Murp hy,

Trevanathan & Y eargin-AUsop, 1995) and demonstrate comparatively slower

development of fine motor skills ( EUiman, Bryan, EUiman, Walker & Harvey, 199 1 ;

Schneck & Henderson, 1990).

Msall et al. ( 1992) reported that the predictors of special education needs at

kindergarten entry were: low socioeconomic aatus, nonwhite race and male gender.

Hayden-Peak ( 1 993) cited specific gender differences m special education programs with

twice as many boys as girls being placed. However, the mcidence of boys born

p rematurely was not found to exceed the mcidence of premature female births and

developmental outcomes at one year were not significantly d.ifEerent (Orgill, Astbury.

Bajuk & Yu, 1982). in summary. aitbough boys made up the majoxity of children

identiiied as developmentally or learning disabled, there was not a greater mcidence of

boys bom prematurely. Outcornes for preterm infants did not appear to be differentiated

on the basis of gender at one year of age.

2.9 Methodological issues

Ayiward and PfeifTer ( 1989) publirhed a review of 8 1 empincal studies fiom the

Literatwe over the past ten years which examined the developmental outcomes of low

birthweight infants. The authors reported a lack of conclusive hd ings in the

developmental outcomes m the preterm population. The subject populations were

heterogeneous, the developrnental influences of home and community environments were

variable. and studies tended to measure Werent types of outcomes. For example. while

most were concemed with cognitive outcomes. others ernphasized motor outcomes and

still others used rating scales which mcorporated cognitive, motor and aeurologic

function into one global rating. There was a lack of uniformity of cut-off scores used to

delineate "normai".

Many studies coafllsed the relative temu of impairment, disability and handicap.

These te= are based on the World Health Organization criteria for i d e n m g different

aspects of health mvohrement. " impairment" was dehed as an underlying deficit m the

23

psychological, physiological or anatomical systems. The deficit m these underlying

systems leads to dysfunction in the abilities which make up the components of daily We.

The WHO criteria used the term "disability" the describe the inability of an inchidual to

carry out the activities of daity living. The tenu '0andicap" implies the societal

consequeoces for the child which manifest as a result ofhis impairments and disabilities

and of society's inabrlity to adapt (Schreuder. Veen, Ens-Dokkum,

Verloove-Vaahorïck, Brand, Ruys, 1992). Uniformdy m the application of these labels

was suggested as a minimum standard to which authors should comply in descniing

developmental compromise.

Aylward and PfeBer ( 1989) aated that. although significantly different fiom

normal control groups, the rnean performance of low birth weight groups was ofien

within the normal range and may not have represented clinically significant or nuictional

differences in performance. This interpretation of relative performance between infants

bom at term and preterm infants differed sigdicantly f?om that of Forslund and Bjere

( 1990). who proposed that the low birth weight children were fùnctioning in a lower

'normai' range characterized by diicuities m eye-hand coordination and other

performance skills important for early learning . Alyward and Pfefler (1989) suggeaed

that outcornes should be presented in a categorical fashion as well as with continuous

data. Siegel had already estabtished a precedent for this m her work on the development

of risk indices (Siegel, 1982). In summary, lack of uniformity m the methodology and

terminology confounds the mterpretation of data fiom different studies.

24

2.10 Corrected and Uncorrected Ages

ûne of the controversies in the literature on foilow up of preterm infmts is

whether to report corrected or uncorrected chronological ages. Siegel ( 1982) suggested

that uncorrected scores be used af€er 12 months, because she found that assessrnent

outcomes of preterm performance d e r bvelve months of age using uncorrected age

scores were correlated to a greater degree with outcomes at age three and age five than

were outcomes based on corrected age. Thus. a more accurate prediction of eventual

outcome was given when uncorrected scores were used afier tweive rnonths of age.

Furthemore, in contrast to the inaccuracies m establiçhmg corrected age, by nibtracting

the mfant's gestational age from 40 weeks, there are no ditnculties in establishing

chronological age.

Siegel, Saigal Rosenbaum, Morton, Young, Berenbaum and Stoskopf ( 1982)

reported that. when corrected age scores were used to interpret the Bayley and ReyneU

Scales, motor scores were the only scores which were lower for the preterm group than

for a comparison group of fulltem children. When uncorrected scores were used.

however, cognitive and language s f l s as weil as rnotor skiils were lower.

Mazer et al. ( 1988) found that locomotor, performance and eye-hand skills on

the GrifEths Scale (GntFths, 1954) decreased with mcreasing chronological age and

were the lowea scores at 36 months uncorrected age. The authors suggested that motor

skills were more adversely affected by low birth weight or preterm birth than language

and personal-social development which were the highest scores by 36 months of

uncorrected age. In their study, the authors used corrected age scores until24 months

25

and subsequently used uncorrected age scores at 36 months. However, they appeared

not to consider Siegel's ( 1983 ) fmding that using uncorrected scores beyond 12 months

resulted m a more accurate prediction. Mazer et al. ( 1988) codd have reported

uncorrected age scores at 24 months m order to more clearly mdicate the trend for

differential development between developmental domains.

Landry. Fletcher and Denson ( 1993) suggested that the use of corrected age

scores created a misleadhg impression of adequate performance which wodd be

detrimental at later stages when the child had not caught up. These authors argued for

the use of uncorrected age scores in order to provide a more realistic evaluation of the

child's performance as well as to indicate whether the child would require intervention. Ln

a study of 75 infants bom weighmg less than 1300 gram, and separated into f k e risk

goups on the bans of severity of brain lesion and respiratory disease, the authors found

that, in the hi& N k groups, the mental development score at 36 months uncorrected age

was moa accurately predicted by the uncorrected age score for mental development at 6

months. Landiy et al. ( 1993) stated that the use of uncorrected scores permitted a better

basis for the realistic education of parents regarding eventual developmental outcome.

In summaiy, there is controversy in the literature about the use of corrected versus

unconected age scores to interpret developmental performance. The use of uncorrected

scores in children d e r 12 rnonths of age reveals a stronger relation to difnculties m

preschool performance.

26

2.1 1 Risk indices

Most previous studies used single variables, nich as ultrasound findings of

echodensity m the firt year of Me, to predict developmental outcome, and found that

they had some predictive utility. However, not every i n d ~ d u a l with severe brain lesions

presented with severe neurological deficits nor did every mdividual who presented with

severe f o m of the other variables associated with prematurity whkh were mvestigated

in isolation. The literature niggeas that the long-tenn outcome of children boni

prernaturely is determined by a number of variables which act mtrinsically and

extrinsically, either alone or m combmation.

Smith, Rick, Femss and Seliman ( 1972) attempted to predict developmental

outcomes in childhood based on the prenataL perinatal, and postnatal course. The study

was conducted with a sample (n = 89) of low SES. black fullterm mfants (mean

gestational age: 3 8.9 weeks. mean birthweight: 2. 99 1.9 grams). Predictors of

developmental outcome included matemal and obnetrical medical history. matemal

demographics (includhg matemal education) and neurological and psychological

evaluations at eight months. one year, four yean and seven years of age. At each

assessment point, the outcomes of the developmental assessment were analysed using

discriminant fhction analysis to determine the degree to which the predictors predicted

a normal or abnormal score. At the next assessment point, the results of the previous

assessment were incorporated into the d i s m a n t function analysis as a predictor. This

strategy provided hcreasingly high rates of prediaive success at enniing t h e periods.

Predictors were found to contniute diaerently to the analysis at different times. For

27

example, while the eight month Bayley Motor Scale contniuted at similar levels at one

year and four years, the Bayley Mental Scale contnbuted more at four years. Although

this snidy was not conducted with preterms, the Ming of the differential predictive

accwacy of variables over the course of development was instrumental in the m e r

development of predictive risk mdices.

Field, Hailock, Ting, Dempsey, Dabiri and Shuman ( 1978) developed a

cumulative risk index in their foilow-up of high risk infants. The risk mdex included

measures of postnatal complication, infant mteractiveness and obstetrical complications.

Three groups of babies were followed at four month intervals during the fkst year of We:

a high risk preterm group with BPD. a high risk poa term group with postmaturity

syndrome. (The preterm group showed motor and mental delays, while the postterm

group showed only mental delays) and a low risk fulltemi group. Using discriminate

function analytis, the authors showed that different predictors correlated with outcornes

at different points in the fust year. The risk index conectly classified infants as at risk

(-434) at one year of corrected age at a rate of 100% for the Bayley mental score and a

rate of 9 1% for the Bayley motor score.

Landry et al. ( 1988) suggested that a combination of medical variables and the

multivariate risk mdex proposed by Siegel et al. ( 1982) would M e r elucidate the

distniution of risk. This risk index for the prediction of learning disabdity in preterm and

full term infants mcluded environmental, demographic, perinatal and reproductive factors.

Siegel et al. 's study mcluded 53 preterm Mfmts (< 1 50 1 gram) and 5 1 £ùilterm mfmts

who were followed for 36 montbs. Investigating medical variables associated with

28

preterm birth? they found additional risks related to bypoxic damage including mcreased

fiequency of apnea, presence of birth asphyxia and degree of respiratory distress. ln this

midy, environmental and demographic predictors were found to be better indicators of

language fùnction, while the perinatal and reproductive predictors were better predictors

of perceptuai motor function.

In a study of healthy, full term children, Molfiese, Helwig and Holcomb ( 1993)

suggested that biomedical factors would have more idluence on development of language

and cognition in the first two years, while environrnental influences would have a stronger

effect at three years of age. In summary, differentiated categones of multivariate risk

factors have been found to predict different aspects of development at different ages in

pre-term as well as fidl term children. in the fkst two years of He, both biomedical and

environmental influences are related to developmental outcome. M e r two years of age.

the environmental influences appear to have a stronger association with developmental

outcome. However, these fïndings do not consider the possiiility that. due to the extreme

f i a m of ELBW preterms and the complexity of the biomedical involvement. the

duration of the relationshq between biomedical factors and developmental outcome could

possibly enend longer than the first two years in these children. In this case, it would be

worthwh.de to examine the relationship between performance skills at three years and a

risk index which mcludes both demographic and biomedical risk variables.

2.12 School Performance Outcomes

The previous sections of the literature review have reported on the effects of

29

prematurÏty during mfancy. Altbough mort ality and severity of morbidity m premanuity

are diminishmg, outcome studies with premature mfants have shown that difEculties in

performance perskt at a more subtle, organizational level which ultimately affects

preschool and school performance. Colin, Halsey, and Anderson ( 199 1 ) found a

pattern of decreasing performance m developmental skills with age among preterm

infants. They suggested that, as the demand for performance mcreased, the children's

capacity for function was exceeded and they began to do less and less well as

envkonments mcreased in complexïty. This pattern of deterioratmg performance was

consistent with the identified pattern of preterm infant behaviour descnied by Als et al.

( 1986)' m which the subsystem balance which underlies the infant's physiological aate

failed when conf?onted with hcreashg stress or demands f?om the environment.

Klein. Hack, Gallagher and Fanaroff(1985) midied 80 VLBW children (< 1200

erams) at h e years of uncorrected age. Of these. 65 were f?ee of neurological C

impairments and scored in the normal range on the Stdord-Binet. The children were

matched with full term age class mates on demographic variables and tested on meanires

of IQ and psycho-educational ski&. While no Merences in IQ were found between the

two groups, significant difference between groups were found on areas of spatial

relations and Msual motor mtegratioo.

M d , Buck Rogers and Catanzaro (1992) reporteci that. of 153 children bom

between 23-28 weeks gestational age, 50% were identified for special education at

kindergarten entry. Iarvena et al ( 199 1) noted that ELBW children at six years of age

bad immature visual motor integration skills, emotional immaturity and language delay.

30

Vohr and Coli (1985) divided 42 VLBW infants mto the following three groups on the

basis of their one year neurological assesment: normal, suspect and abnormal. At age

seven, 58% of the suspect group and 87% of the abnormal group were reading below age

level. Children fiom ail three groups showed difEculty with visual-motor mtegration.

Hack et al. (1994) found poorer academic achiwement as measured by the Woodcock

Johnson Tests of Achievement -Revised (Woodcock & Mather, 1989) in children bom

under 750 grams when compared to another group of preterms weighing 750 - 1499

grams as well as a group of fùll term gifants. In çummary, minor and major impairments in

ELB W preterm's developmental abilities appeared to affiect visual motor and possibly

spatial mtegration skills, which may have implications for school performance.

2.13 Conclusion

Many factors are associated with the developmental outcome of the ELBW

infants. Given the numbers of nsk factors which influence the developrnental outcomes of

prematurity, a multivariate andysis would improve the ab- to predict developmental

outcomes by simultaneously analyshg severai of these risk factors (Kirk, 1989).

hproved suMval rates and the decrease in the incidence of major neurological

dysfunction have made the study of the multivariate association between typical risk

factors and developmental outcomes of ELBW infants more feasile. Early studies of

school age outcomes indicate that these children have specific difnculties even though

they may be functioning within the normal ranges of school testing. Few studies have

examined preschool outcomes to determine a profile of developmental strengths and

weahesses at that age. T'us, the objectives of the present study are: to examine the

3 1

relationship between risk factors and develop mental outcome in motor and preschool

performance domains; to compare the performance of ELBW preschoolers on

developmental outcome measures with published n o m ; to identify a profile of relative

strengths and weaknesses in ELBW preschool performance.

2.14 Statement of Eiypotheses

The general hypothesis to be tested by this study was that detailed assessrnent of

motor and organizational skills of healthy ELBW preterm children at three years of age

would reveal subtle impairrnents, and that performance levels would be positively

correlated with birthweight and negatively correlated with the seventy of risk conditions

present during the perinatal penod.

The speciiïc hypotheses to be teaed are: There will be a direct relationshrp between

preschool performance skills of ELBW premature mfants and:

- birthweight

- gestational age

- N e for gestational age

- socioeconomic status

There wül be an inverse relationship between preschool performance skiUs of ELBW premature

infants and:

- the presence of brain lesion

- the presence of bronchopulmonary dysplasia

- the number of days ventilated during hospitalization

- male gender

Chapter ïII

METHOD

3.1 Subjects

The regional sample consisted of 105 ELBW preterm infants participating in a

longitudinal neonatal follow-up program who had no diagnosis of major impairment:

cerebral palsy, mental retardation, bhdness or deafness. The children were teaed at a

corrected age of three years according to the existmg protocol of the Foilow-up Clhic

in Metropohan Toronto. Corrected age was established by subtracting the infant's

gestational age fkom 40 weeks. Two tertiary acute care Neonatal Intensive Care Uoits

(MCU) acted as the source of infants for follow-up. One nursery (n = 58) was an mbom

NICU where infants were bom in the hospitai and transferred to the NICU as a r e d t of

their hi& risk status. The other nursery (n = 47 ) was the referral outbom MCU of a

teniary acute care pediatnc hospital where high risk infants were transported f?om

community hospitals on an emergency basis for intensive care. There were 49 male

children and 56 female children m the sample. The mean uncorrected age of the children

at teaing was 40 months. The ethnic origin of the sample was Iargely Caucasian; 1 I of

the children were Black, 3 were of East Indian origin, 2 were of Asian ongin.

33

3.2 Measures

Scores for the children were calculated on the basis of their uncorrected age as

well as on their corrected age. Motor performance was assessed on the Peabody

Developmental Motor Scales (PDMS) -Grass Motor and Fine Motor Scales (Folio,

1974). Developmental Motor Quotients (DMQ), based on a mean of 100 and a standard

deviation of 15. were reported for the PDMS Gross Motor (DMQ-GM) and Fme Motor

Scales (DMQ-FM). The Miller Assessrnent for Preschoolers (MAP) was used to assess

preschool performance skills (Miller, 1982). These measures will be descnibed in detail

below.

3.2 1 Peabody Develqmental Motor Scales (PDMS)

The PDMS has been found to be a valid measure of motor development

regardiess of gender or race of the child (white and non-white: blacW Hispanie)

(Hinderer, Richardson & Atwater, 1989). although ao Asian or native children were

included in the normative sample. A sample size of 6 17 subjects was used to standardize

the test. Measures of test-retest refiabihy, mterrater reliability and standard error of

measurement established that the PDMS was stable over time and between raters

(test-retest reliability: -95 ; interrater reliability coefficients: -97; standard error of

measurement : [1.10-5.391).

Criterion-related validity, constnict validity, concurrent and predictive validity

were estabfished between the Bayley and the PDMS. Constnict validity showed that the

test discriminated between children with normal and delayed motor development except

at the 0-5 month level on Gross Motor (GM) and Fme Motor (FM) scales. There were

moderate to high co~elations (.63 to .93) behhreen Bayley Motor and PDMS-GM which

34

showed that the test had good concurrent validay (Folio, 1974). Studies of content

validity indicated that the measure provided an adequate representative sample of fine

and gross motor skills (Hinderer et ai., 1989).

Both the Gross Motor and Fme Motor Scales of the PDMS were anministered to the

sample. The Gross Motor Scale measured four skius: Balance, Nonlocomotor, Locomotor

and Receipt and Propulsion. Balance mvoived standing on one foot, walkmg a balance beam

and walking on tiptoe. In the Locomotor skiU task, the child was required to demonstrate a

smooth transition fiom a Sitting to a standing position. Locomotor items invohed that the

child walk down stairs ushg reciprocal leg movements without a m support, jump over

hurdles without tripping, jump down landmg on two Teet, hop and skrp. In the Receipt and

Propulsion skill task, the child was required to kick and catch a ball.

The Fine Motor Scale measured four skills; Grasping, Hand Use, Eye-Hand

Coordination and Manual Dexterity. Grasping invohed holding a marker using an age

appropriate grasp. The Hand Use subtea assessed hand preference by observing which

hand the child used to pick up a block on consecutive trials. The ability to remove a tight

fitting cap fi-om a bonle was also assessed. Eye-Hand Coordination required the child

to build a block tower, a block bridge, copy a circle, cut paper, cut dong a line and copy

a cross. Manual Dexterity examined the abhty to unbutton buttons, string beads and

wind a toy.

3.22 MiUer Assessment for Preschoolers (MAPI

The Miller Assessment for Preschoolers (MAP), a developmental test

constmcted for the purpose of identifjing children at moderate to severe nsk for fùture

school-related problems (Slaton, 1985), was used to assess preschool performance skills.

35

DeGangi ( 1983) found that the test was weU developed in terms of item disahination,

content validity, inter-rater reüability md test re-test reliabüity. Criterion-related validay

measures were established between the MAP and the Weschler Freschool and Primary

Scale of Intelligence as well as the MAP and the Denver Developmental Screening Test.

The sample (n= 10 14) of normal children aged 2.9 - 5.8 years was chosen ushg a

random and aratified procedure with equal distriiutions obtained for each age group as

weil as sex. U.S. Census Bureau figures were used to determine distributions for

socioeconomic status and regional representation. There was equal distribution for age

groups se% region of the United States and socioeconomic natus. Content validity

studies showed that the different subtests measured distinct hc t ions of the child's

performance. Test items contniuted significantly at <.O I level and subtea indices

contributed equaliy (A47 to .778). Test items were iocluded in the MAP (271500 items)

based on item difficulty (percentage of items passed), item discrimination (point biserial

correlation of each item) and correlation snidies (relationship among items and the

subtea categories). Ody items which discriminated among the lowest 20% of the normal

sample were selected. These items also discrimhated well across age groups.

Developmental abilities measured were Foundations (sensory and motor

abilaies), Coordination ( h e , gross and oral motor), Verbal skills (expressive and

receptive language), Nonverbal skills (sequencing, memory and visual-spatial perception)

and Complex Tasks (which invohed two or more abilities).

The Foundation hdex was designed as an examination of neurological

function and sensory motor status. Three years olds were expected to complete two test

items whicb tapped touch discrimination by excludmg the use of vision . The children

36

were asked to iden* familiar objects (bail, spoon) by touch (Stereognosis) and to

identG which h g e r had been touched (Fmger Identification) while their eyes were

shielded. The Hand Nose task required the child to altemate accurateiy between

touchmg his nose and a puppet with eyes open and then with eyes closed. The Stamp

Game teaed rapid altematmg movements of the lower extremities while maintainhg

sitting balance. The Romberg task assessed the child's postural stability by asking him or

her to stand like a statue with eyes closed for 15 seconds. Obseivations for postural

compensation during transitional movements were made in the Kneel Stand item whieh

required the child to move from half kneeling to standing in a smoothly executed

movement. The Stepping task required the child to march in one spot without deviation

Born the narting pomt or rotation of the tnink. The Vertical Writing task asked the

children to hold a p e n d and draw a vertical line on a page as ifa bunny was hoppmg

into his house. The Waiking Game required the child to demonstrate wallchg on a line

leavine a s w i l space between the heel and toe foot placement.

The Coordination index measured gross, h e and oral motor coordination.

Performance on the Vertical Wnting, Walking Game and Stamp Game items were also

scored for this subtest. ChiIdren were asked to build a block tower. Fme Motor

Accuracy was assessed by a s h g the child to draw vertical lines wahm two paraliel lines

(Draw-a-Cage Game). Oral motor coordination was assessed by a s b g the child imitate

movements in superior, Siferior, lateral and circular planes. Further observation of oral

motor coordination was made m the Articulation item which asked the child to repeat

words which contained targeted sounds at the begbnhg and the end of each word

(e.g., moei, -h-, cal, now, Pcue). Phonological awareness was also required for the

37

child to successfully repeat the targeted sounds m each word.

The Verbal Index was designed to measure expressive and receptive laoguage

skills. Children were asked to look at pictures and answer questions üke: "Which one is

big?". "What do you use to cut with?". Other items mcluded "Why do we have beds?".

"The shy is up; the floor is ." Ability to foliow simple directions was assessed

("Put the penny m the box", "Put the penny on the box") This item also tapped the

child's skills in responding to temporal order. Failure on this task codd also be attnibuted

to mernosr. Children were required to repeat sentences m the correct order and tense as

well to repeat a series of digits.

The Nonverbal Index measured memory and visuai-spatial perception. The

children were required to demonstrate ab- in object memory, simple p d e s and a

figure ground task. The object memory task invohed displaying familiar objects (a b a l a

spoon. a fork, a rubberband, a pencil, a penny) c o v e ~ g the display and removing one

object. The child was then required to remember which object had disappeared. The

p d e s were simple two piece puzzies of a dog and a coat. In the figure ground task,

children were asked to h d simple pictures which were hidden m a larger picture scene.

It should be noted that the skills tested by the Nonverbal Index were not entirely

nonverbal in nature, as verbal l a b e h g was also used in completing the tasks.

The Cornplex Tasks index mchided tasks which mvohed combining visuai

spatial and motor planning abilities in order to successfully complete the tasks. For

example, completion of two block designs using three blocks was required. Two blocks

formed the base of the design in both. In the Chair, the third block was placed directIy

over the block on the right. In the Hat, the third block was placed in the middle of the

38

two bottom blocks. In the Imitation of Postures task, children were asked to imitate

postures by placing &eir hands on their hrps over their heads and on their knees after

observing the examiner demonstrate the required posture. Manipulation of a flat box

maze m order to move a small boit fiom one end to the other was the ha1 item m the

Cornplex Tasks Index.

3.23 Risk Index Variables

Eight predictors of preschool performance outcome were used. Brain Lesion

status was determïned by a minimum of three ultrasound recordings: the £ira taken m

the bst week of life, the second between the second and tbXrd week of We and the third

between the fourth and sixth week of Ne. AU head ultrasound scans to deternine the

presence or absence of intraventricuiar haemorrhage (MI) andlor periventricdar

leukomalacia (PVL) were read by at least two independent observers and- where

conflicts arose, consensus was reached after re-reading. Children with a hiaory of no

lesion were given coding categories of zero (O), children with a history of IVH were

coded as one ( I) , children with a history of PVL were coded as two (2), children with a

history of both PVL and IVH were coded as three (3).

Birthweight (BWt) was measured in grams at the tirne of birth. Socioeconomic

status (SES) was represented by the number of years of matemal education. Children

were considered SmaU for Gestational Age (SGA) when their birthweight was two

standard deviations less than the mean for gestational age based on the Usher-McLean

curves for a Canadian çample (Uher & McLean, 1969). The presence or absence of

Bronchopulmonary Dysplasia (BPD) was made on the basis of radiographie evidence at

the time of discharge f?om the hospital. A clinical diagnosis of BPD was made when the

39

chea X-ray showed thickened a!!eolar septae, cystic changes and unequal aeration of the

lungs with hyperexpansion (Northway, 1979). Children who were diagnosed with BPD

were @en a coding categoiy of one ( 1). Children without BPD received a code of zero

(0 ).

The total number of days that the infants received mechanical ventilation was

counted (#days) and entered as a continuous variable. Information on Gestational Age

(GA) was determined using the clinical method descnbed by hibowitq Dubowitz and

Goldberg ( 1970).

3.3 Procedure

As a part of the longitudinal follow up study, a cohon study design (Borg & Gall

1983) using regession analysis was used ~II order to assess the correlations between the

risk factors and subsequent preschool performance s M s . Data fkom the medical

records were collected on the sample to document birthweight, gestational age.

presence or absence ofbronchopulmonary dysplasia. brain lesion, the number of days

ventilated during the hospital stay, gender, size for gestation age and socioeconornic

status. Preschool performance data on standardized test measures was collected fiom the

occupational therapy report on the medical record. Smce the original data had been

scored according to corrected age, the data were re-scored for performance using

chronologica~ that is, uncorrected age. This was possible for the Peabody Motor Scales

and for the Foundations, Coordmation and Nonverbal Indices of the Miller Assessrnent

for Preschoolers. It was not possible to re-score the Verbal or the Complex Tasks

Indices of the MAP since the performance d e n a for the chronological age group had

40

different task requirements which were not administered at the time of the assessment.

While ali 105 children compieted the PDMS, twenty two of the children did not

complete the MAP due to the time constraints imposed by the hospital clinic schedule. A

total of 83 subjects completed both tests.

3.4 Data Analysis

The data Born the two subgroups of inbom and outborn subject groups were

compared on the eight risk predictors in order to determine if the outbom nursery had

a population of childxen at greater medical nsk because they had been transported to the

nursery as a result of their poor medical status. The two groups were also compared on

preschool performance indicators. Means standard deviations and ranges were

comput ed for each rneasure. T-tests and Chi-square analyses, as appropriate, were

conducted to determine if status on risk predictors was signifiicantly difEerent between

the two nurseries. T-tests were conducted to determine ifperformances on the

outcomes variables was si@cantiy different between the two nurseries.

The sample was then aoalysed as a whole to take advantage of the statistical

power of the sample size. The descriptive analysis was repeated and tests were

conducted to compare the entire sample to a standardized n o m Stepwise regression

analyses were conducted to detennine which risk predictors had the highest partial

correlations with outcome variables. Logistic regression analysis was conducted to

determine the pomt at which the maximum number of cases were correctly classified by

the risk index mto high and low scoring groups. SensitMty and specificity rneasures were

calcdated for the outcomes which had the highest rate of correct classification.

Chapter n7

RESULTS

4.1 Data Analysis for Two Nursery Groups

The data of the two subgroups of subjects who were hospitalized m mbom and

outbom nurseries were examined reparately ushg the eight risk prediaors of outcorne:

brain lesion on ultrasoumi, the presence or absence of BPD, gestational age? number of

days ventilated during hospitakation, birthweight, gender, whether the child was

appropnate or small for gestationai age (AGAISGA) and socioeconomic status (SES).

The two nurseries were compared to deterutine ifthe outbom nursery may have had a

population of children at greater medical N k who had been transported to the nursery

as a result of their poor medical status.

4.1 1 Means. Standard Deviations. Ranges of Risk Predictors and Preschool

Performance Outcornes Between Nurse- Groups.

Descriptive statistics (means, standard deviations, ranges on each nursery group)

are provided on ail of the continuous predictor variables (see Table 1). Peabody Motor

Scales, (see Table 3) and the Miller Assesment for Preschoolers measures

(see Table 4). Frequency distributions are provided for ail the categoncai predictor

variables (brain lesion, BPD, gender, SGA [see Table 21). The outbom nursery was

identified as Nursery 1 and the inbom nursery was identified as Nursery 2.

TABLE 1 Descriptive Statistics for Predictors by Nursery

Predictor Nursery Mean Standard Deviation Range p <.O5

Gestational Age 1 26 1.8 23-32 .O04

# Days Ventilated 1 54 29 1-160 .O00 1

Socioeconomic S tatus (# years materna1 sducation)

Note. Nursery 1 = Outborn Nursery; Nursery 2 = inborn Nursery. ns = nonsignificant result

TABLE 2 Descriptive Statistics for Predictors by Nursery

Nursery 1 Nursery 2 (Outborn) (Inborn)

Brain Lcsion No Lesion

Bronchopulmonary present Dysplasia (BPD)

not present

Gender male

Srnall for Gestational SGA A%e

Note: ns = nonsignif~cant result -

T.%BLE 3 Descriptive Statistics for Peabody Motor Scales for Correcteci Age (CA) and Uncorrected Age (UA) by Nursery

Outcorne Correcteci/ Nursery Mean Standard Range p <.O5 Measure Uncorrected Deviation

Gross Motor CA 1 84. O 13.0 65.0- 110.0 ns Scales

2 83.0 11.0 65.0- 1 10.0

Fine Motor CA 1 81.0 14.0 65.û- 1 14.0 11s Scales

7 - 83.0 13.0 65.0-1 11.0

7 - 82. O 13.0 65.0-1 1 1.0

ns: nonsientficant result

TABLE 4 Descriptive S tatistics for Miller Assesment for Preschoolers for Corrected Age (CA) and Uncorrected Age (UA) by Nursery

Outcorne Measure Correctedl Nursery Msan Standard Range p < .O5 Uncorrected Age Deviation

Foundations Scale CA 1 33.0 24.0 2.0 - 99.0 .O00 1 (Voile)

7 - 58.0 30.0 9.0-99.0

Coordination Scale ( Y i e )

Verbal Scale (%de)

Nonverbal Scale (?/de )

CompIex Tasks Scale (Voile)

Total Score CA 1 3 1.0 30.0 2.0 - 99.0 . 04

(%de) 2 54.0 27.0 6.0-92.0

Note: Nursery 1 = Outborn Nursery; Nursery 2 = Inborn Nursery ns = n o n ~ i ~ c a n t result

46

4.1 2 Cornparison of Nursery Grou~s on Risk Predictors.

T-tests and Chi-square analyses were conducted to detemine if status on nsk

predictors was sigdicantly different between the two nurseries (see Tables 1 and 2).

There was no significant difference m birthweight between nurseries. Mean gestational

age was significantly different, with the gestational age m Nursery 2 higher than m

Nursery 1. The infants Grom Nursery 2 were ventilated for significantiy fewer days

than those fiom Nursery 1, the SES of Nursery 2 was significantly higher than Nursery

1 and Nursery 2 had a sigrilficantly lower incidence of brain lesion and BPD. There

was no sigiilficant clifference between the nurseries in gender or the incidence of infants

who were SGA These analyses showed that the mfants in Nursery 1 had significantly

increased mcidence of low gestational age, number of days of mechanical ventilation.

brain lesion, bronchopulmonary dysplasia and lower socioeconomic status.

T-tests were used to compare preschool performance outcornes of the two

nursery groups. There was no significant difference between nurseries on the Gross

Motor Scale of the Peabody Motor Scales for either corrected or uncorrected age. There

was no dinerence on the Fme Motor Scale ushg corrected age scores. T'here was a

agnificant difference between nurseries on the Fine Motor Scale using uncorrected age

scores with Nursery 2 scoring higher than Nursery 1 (see Table 3).

Sigruficant ciifferences between nurseries were found on the Foundations Index

for corrected age and uncorrected age and on the Coordination Index for corrected age

and uncorrected age. No significant difference between nursenes was found on the

47

corrected or uncorrected scores on the Nonverbal Index corrected age scores on the

Verbal Index, or corrected age scores on the Complex Task Index. Sigxufïcant

Merences were found on the corrected score for the Total Score Index. Uncorrected

scores were not available for the latter three mdices (see Table 4).

These data indicated that the children in Nursery 1 were at greater medical nsk

in h e out of eight risk predictors ( excluding birthweigbt, gender and size for gestational

age). These children had been transported to the outbom nursery h m their birth

hospitals as a result of their poor medical aatus. An analysis of preschool performance

outcomes between the ~ W O nurseries showed that the Nursery 1 children performed

sigdicantly more poorly than their Nursery 2 peers on fine motor skills as measured by

uncorrected age scores on the Peabody Motor Scales and corrected as weli as

uncorrected age scores on the Foundations and Coordination Indices of the Miller

Assesment for Reschoolers. However, performance Merences on the NonverbaL

Verbal and Complex Task Indices were not signiticant.

4.14 Comoarison of Pre-school Performance Outcornes of Nurse- G r o u ~ s to

a Standardized N o m

T-tests were used to compare preschool performance outcomes to a

standardized n o m Performance on the Peabody Motor Scaies was significantly below

the population mean of 100 on both the Gross Motor Scaie for corrected age and

uncorrected age as weli as the Fme Motor Scaie for corrected age and uncorrected age.

AH groups scored significantiy below the population mean (see table 5).

TABLE 5 Cornpaison of Peabody Motor Scales for Comcted Age (CA) and Uncorrected Age (UA) by Nursery to a S tandardized N o m

Outcome Measure Corrected Age/ Nursery Uncorrected Age

-- -

Gross Motor Scales

Fine Motor Scales

49

T-tests were used to compare Miller Assessment for Preschoolers outcornes for

CA and UA scores for each nursery to a standardized n o m Performance ciifferences on

the Miller Assessrnent for Preschoolers (MAP) were more variable and depended on

whether corrected or uncorrected ages were used. Performance on the MAP was

si&cantly below the fiftieth percentile on two of the CA scores and three of the UA

scores for Nursery 1. For Nursery 2, the Coordination CA score was significantly below

the mieth percentile. while the Complex Tasks CA score was signdîcantly above it. One

UA score was significantly below the m e t h percentile (see Table 6).

TABLE 6 Cornparison of Miller Assessrnent for Preschoolers for Correctecl Age (CA) and Uncorrected Age (UA) by Nursery to a Standardized N o m

Outcome Measure Correctedl Nursery p < .O5 Uncorrected Age

Foundations Scale (%de)

Coordination Scale (?&ie)

Verbal Scale (Ohde)

Nonverbal Scale (?hile)

Complex Tasks Scale (Yde)

Total Score CA 1 n s

(%de) 7 - ns

ns: nonsignificant result

Note. Nursery 1 = Outbom Nursery; Nursery 2 = inborn Nursery.

4.2 Data Analysis for Cornbined Nurseries

Although there were sipifkant differences m perinatal risk and preschool

performance between nursery groups, these differences were interpreted as bemg typical

of the range of perinatal expenence of the ELBW population as a whole. The sam.ple

was analysed as a whole to take advantage of the aatistical power of the large -le

Ne. The data sets fiom both nurseries were combmed and the descriptive analyçis was

coaducted on the sample as a whole.

4.2 1 Means. Standard Deviations. Ranges of Risk Predictors and Preschool

Performance Outcornes for Combmed Nurseries

Descriptive statistics (means. standard deviations, ranges on each nursery group)

are provided on ali of the continuous predictor variables (see Table 7), Peabody Motor

Scales, (see Table 9) and the Miller Assessrnent for Preschoolers ([see Table 10).

Frequency distributions are provided for ali the categorical predictor variables (brain

lesion. BPD. gender, SGA [see Table 81).

TABLE 7 Descriptive Statistics for Predictors- Total SampIe

Predictor Mean Standard Deviation Range

Grstational Age (weeb)

# Days Ventiiated

Socioeconomic S tatus (# yrars materna1 education )

TABLE 8 Descriptive Statistics for Predictors- Total Sample

Predictor Status Frequency

Brain Lesion No Lesion 46%

PVL f 4%

IVH 33%

Broncho-puhonary Dysplasia (BPD)

Gender

Smaii for Gestational Age (SGA) I Appropriate for Gestational Age (AGA)

prrsent

not present

male

female

SGA

AGA

TABLE 9 Descriptive Statistics for Peabody Motor Scales for Corrected Age (CA) and Unconected Age (UA) - Total Samp le

Outcome C orrectedf Mean Standard Deviation Measure Uncorrected Age

Gros Motor CA Scales

(DMQ) U A

Fine Motor CA Scdes

( DMQ) UA

TABLE 10 Descriptive Statistics for Miller Assessrnent for Preschoolers -Total SampIe

Outcome Correctedl Mean Standard Deviation Range Masure Unconected Age

Foundations CA (?hile)

Coordination CA (?hile)

Verbal (%de)

Nonverbal (%de)

Complex Tasks (%de)

Total Score CA 47.0 (%iIe)

54

4.22 Total Sawle: Cornpansons of Reschool Performance Outcornes to a

Standardized Norm

In order to analyse the results of the outcomes of preschool performance m the

sample as a whole, T-tests were used to compare preschool performance outcomes to a

standardized n o m The PDMS was compared to a Developmental Motor Quotient of

100 and the MAP Indices were compared to the 50th percentile as bemg normal.

Performance on the Peabody Motor Scales was significantly below the

Developmental Motor Quotient (DMQ) of LOO on the Gross Motor Scale for both

corrected age and uncorrected ages welI as the Fme Motor Scale for corrected age and

uncomected age (See Figure 1, Table 1 1). No significant merences were found for the

Foundations index or the Coordination Index ushg corrected age scores. However.

sigiilficant clifferences fkom the n o m were found using uncorrected age scores. The

corrected age score of the Nonverbal Index was above the 50 percentile. but not

sienificantly so. However. uncorrected age scores on the Nonverbal index were

significantly below the 50th percentile. Scores on the Verbal Index and the Cornplex

Task index were significantly above the 50th percentile (corrected age only). No

sipuficant difference was found on the Total Score Index (See Figure 2 and Figure 3.

Table 1 1).

Figure 2 Miller Assessrnent for Preschoolers

Foundations (FI), Coordination (CI). Nonverbal (NW) Indices

Cornparison of Means Corrected Age (CA) I Uncorrected Age (UA)

Fi CI NVI

Figure 3 Miller Assessrnent for Preschoolers

Verbal (VI), Complex Tasks (CTI), Total Score (TSI) Indices

Comparison of Means Corrected Age (CA)

TABLE 1 I Cornparison of Peabody Motor Scales and Miiier Assessment for Preschoolers To a Standardized Nom for Corrected Age (CA) and Uncorrecteci Age (UA): Total Sample

Outcome Measure CorrectedlUncorrected Age P

Peabody Motor Scales

Gross Motor Scaies

Fine Motor Scales

Miller Assessment for Preschoolers

Foitndations index

Coordination index

Nonverbal Index

Verbal index

Cornplex Tasks Index

TotaI Score Index

ns: nonsigndicant result

4.23 Stqwise Remession Anahsis

Regression analysis using the eight predictor variables was conducted for each of

the seven outcome variables. Stepwise regressions were done to determine which

predictors had the highest partial correlations with the outcome variables. (See

Appendices A to D for tables of simple correlations) Variables needed an F of 1.0 to be

entered. The procedure was chosen as it provides the mon parsimonious regression wRh

the least number of variables.

Tables 12- 14 nimmarize the mdividual regressions. The analysis showed that,

for the PDMS Gross Motor Scales (CA and UA), BPD contniuted the greatea partial

correlation to the regression equation, but these were not significant. For the MAP

Verbal index, BPD agam conuiiuted the greatest partial correlation to the regression

equation. but this was not significant. AU other regression equations had at leaa one

risk variable which contniuted signiticantly to the equation.

Tables 15- 17 summarize the contributions made by the predictors to the

regression equations. The predictor which made a significant contribution to the moa

number of equations was Bronchopulmonary Dysplasia (BPD). This variable was a

&9nificant predictor of the MAP Foundations Index (corrected and uncorrected ages),

Coordination Index (uncorrected age), Nonverbal Index (uncorrected age) and the Total

Score index (corrected age). The presence of BPD was always associated with lower

scores on ail of these outcome measures.

Gender made an independent contnbution to the Peabody Fme Motor Scale

(corrected and uncorrected age:p < .Ol), the MAP Nonverbal Index with corrected

60

age: (a< .Oz), and the Complex Tasks Index with corrected age (p < -02). In all cases.

boys perfonned more poorly.

Birthweight made a significant contribution to predining the Peabody Fine

Motor Scde (corrected age), the MAP Foundations Index (uncorrected age), and the

Nonverbal Index for both corrected and uncorrected ages. The lower the birthweight.

the lower the scores on these outcomes,

Gestational Age was significantly correlated with the Fine Motor Scale of the

Peabody Motor Scaie (uncorrected age) as weil as the Complex Tasks Index (corrected

age). Socioeconomic status was sigdcantly correlated with the MAP Complex Tasks

Index (corrected age). Number of days ventilated was significantly correlated with the

MAP Coordination Index (corrected age).

Five outcome variables had significant partial correlation with two predictors.

Gender and Birthweight both had significant partial correlations with the Fine Motor

Scale of the Peabody Motor Scale (corrected age) as weil as the MAP Nonverbal index

(corrected age). Birthweight and BPD were both si@cantly correlated with the

Foundations Index (uncorrected age) as well as the Nonverbal Index (uncorrected age)

(see Table 13). Gender and Gestationai Age were both signincantly correlated with the

Fine Motor Scale of the Peabody Motor Scale (uncorrected age) .

The MAP Complex Tasks Index had significant partial correlations with three

predictor variables: Gender. Gestational Age and SES.

Bram Lesion and SGA were not significantly correlated with preschool

performance outcomes in any of the stepwise regession analysis.

TABLE 13 Summary of Stepwise Regression Correlation and Variance Results on Peabody Scales for Corrected (CA) and Uncorrected Age (UA)

- -- - -

Outcome Correctd Predictor Cum Cum Adj usted R' C hangr ui RI Measure Uncorrected r R2

M e

Gross Motor CA Scales

BPD

Fine Motor Scales

Brain Lesion

UA BPD

CA Gender

BWt

Brain Lesion

GA

Gender

SGA/AGA

Brain Lesion

.03*

.01

OS*

O3 *

.02

.O 1

TABLE 13 Summary of Stqwise Regressions Correlation and Variance Results on Miller Assessrnent for PreschwIers for Corrected (CA) and Uncorrecteci Age (UA) for Foundations, Coordination and Nonverbal indices

Outcome Measure Corrected/ Predictor Cum Cum Adjusted R' Change in R' Uncomected Age r R'

- -

Foundations Index CA BPD .26 .O7 . 06 .O6 *

B r a i Lesion .3 1 . I O .O7 .O1

BWt .34 .12 .OS 0 1

Gender .36 .13 . OS O0

BPD .36 .13 .12 .12 *

BWt -42 .18 .16 .W *

Brain Lesion -44 .19 .16 . O 1

Coordination Index

Nonverbal Index

# days

BPD

Brain Lesion

SES

BPD

Brain Lesion

# days

BWt

BWt -36 -13 .I2 .12 *

Gender -34 .19 .17 .O5 *

#day s -45 .2 1 .18 .O 1

UA BWt -44 .19 .18 . 1 S*

BPD .5 1 -26 .24 .O6 *

TABLE 14 Summary of Stepwise Regressions Correlation and Variance Results on Miller Assessrnent for Preschoolers for Corrected (CA) and Uncorrected Age (UA) for Verbal Complex Tasks and Total Score Indices

Outcomz Measure Correcteci/ Predictor r R' Adjusted R' Change in R' Uncorrected

Age

Verbal Index CA BPD .17 .O3 .O2 .O2

SES .24 .O6 . 03 .O 1

SGAIAGA 2 7 .O8 .O4 .O 1

GA .32 .IO .OS .O 1

Complex Tasks index

Total Score Index

GA .33 . I I .IO .IO *

SES .JI .17 .15 .O5 *

Gender .38 .23 .20 .O5 *

SGAiAGA .5 1 .26 .22 .O2

#days .52 .27 .22 .O 1

BPD .30 .O9 . OS .OS *

Gender 35 .12 .IO . O?

BWt .39 -15 .12 .O2

TABLE 15 Sumrnary of the Results of Stepwise Regression Correlation and Variance for Predictor Variables on Peabody Motor Scales for Conected Age Scores (CA) and Uncorrected Age Scores (UA)

Gros Motor ScaIe Fine Motor Scale

Predictor r Adj R2 r Adj R2 r Adj R2 r Adj R'

BPD .14 .O1 .18 .O2

Brain Lesion -19

Gender

# days

SES - -

GA -

TABLE 16 Summary of the Results of Stepwise Regtession Correlation and Variance for Predictor Variables on M e r

Assessrnent for Prescboolers for Correcteci Age Scores (CA) and Uncorrected Age Scores (UA) : Foundations. Coordination and Nonverbal indices

- - - - ---

Foundations index Coordination index Nonverbal Index

Prèdictor r A ~ J r Adj r Adj r Adj r Adj r Adj R' R2 R2 R' U2 RI

BPD .26

B irthweight -34

Brain Lcsion .3 1

SGAIAGA

Gender -36

# days -

SES

GA

TABLE 17 Summary of the Results of Stepwise Regressioa Comelatioo and Variance for Predictor Variabies on Miller Assessrnent for Preschoolers for Corrected Age Scores (CA): Verbal, Cornplex Task and Total Score Indices

Verbal index Cornplex Tasks index Total Score

Predictor r Adj R' r Adj R2 r Adj R'

BPD

Brthweight

Brain Lesion

SGA/AGA

Gender

# days

SES

GA

67

4.24 Los& Remession Analysis

Logistic regression analysis using the eight predictor variables was conducted on

each of the seven outcome variables to deterrnïne the point at which the maximum

number of cases was correctly classified k to high and low scoring groups. Logistic

regression was selected since t is designed to carry out regression analysis on

dichotornous dependent variables when the predictor variables are both conthuous and

categorical (Norman & Streiner, 1994). In order to conduct this analysis, the seven

dependent variables were re-coded as dichotomous outcomes.

On the Peabody Scales, the sample mean was used to clas* the subjects into

hi& and low scoring groups. as it was one standard deviation below the standaràized

mean and therefore classified the subjects into a clinicaily relevant range of high and low

scores.

On the Miller Assessment for Preschoolers, the median was used as a

classification point, since the median divides the distriiution equally. in order to

determine an optimal method of classification, the median point was treated in two ways

during the analysis: one method included the scores at the median (less than or equal to

and greater than the median FE/GT]) in order to class@ the subjects into a dichotomy

of highest and lowea scores. The second method used the scores which were less than

and greater than the median (LT/GT) m order to classfi the subjects into more extreme

ranges of high and low performance. in the second method, subjects who scored at the

median were not included m the analysk (See Table 18 - Table 23).

68

The classification rate for the PDMS-GM (CA and UA) was below 55 percent

with no predictors entering the equation. The PDMS-FM (CA and UA) showed a

moderate rate of classincation (See table 19). Gender entered the equation for both CA

and UA scores (see Tables 18 and 19). Scores on the MAP Foundations Index (CA and

UA) were also con-ectly classified at a rnoderate rate (See Table 2 1 ). Different

predictors entered the CA and UA regression equation at levels of significance. For the

MAP Coordination Index (CA and UA), the corrected age score correctly classified the

risk predictors m 75 percent of the cases when median scores were excluded. Both

Bram Lesion (3 < -00 1) and BPD (p < -02) significantly contributed to the

classification of outcome scores on this measure. The MAP Nonverbal Index (corrected

age score) was correctiy classilied by the risk predictors m 80 percent of the cases

when median scores were excluded. Birthweight (p < -00 1) and Gender (p < -022)

made siflcant contniutions. The MAP Nonverbal Index (uncorrected age score) was

correctly classified by the risk predictors in 79 percent of the cases when median cut-off

scores were included. Birthweight (4 < -00 1) and #Days Ventilated (p C.002)

sipdicantly related to classZication on this outcome measure (see Tables 20 and 2 1 ).

The MAP Complex Tasks Index (corrected age score) was correctly classifïed by

the risk predictors in total of 80 percent of the cases when median scores were

excluded. Birthweight (p < .002), Brain Lesion (p < .O 13) and Gender (p < .O 14) were

significantly related to the classification. The Verbal Index was classified at a low rate

by the risk index and no predictors entered the logistic regession equation. The Total

69

Score Index was classified at a moderate rate and BPD was the nsk predictor which

contributed ngnifi~antly to the logistic regression equation (see Table s 22 and 23).

In summary, the PDMS -GM and the MAP Verbal Index were classilied at a low

rate by the risk mdex m a logistic regression analysis. Outcornes which were moa

accurately classified were MAP-Coordination (CA), Nonverbal (CA and UA) and

Complex Tasks Indices.

TABLE 18 Peabody Motor Scales: Summary of Results of Logistic Regression for Predictors Entering the Equation Using Corrected (CA) Scores and Uncorrected Age (UA) Scores

P - - - -- .

Gross Motor Scale Fine Motor Scale - - --- - - -

Predictor CA UA CA UA

BPD

B irthweight

Brain Lesion

SGAiAGA

Gender

# days

SES

GA

TABLE 19 Peabody Motor Scales Logistic Regression : Percentage Rate of Correct Predicted Classification Using Corrected Age (CA) Scores and Uncorrected Age (UA) Scores

Gross Motor Scales Fine Motor Scales

Predicted Rate 53.3 51.4 68.6 70.5

Table 20 Miiler Assessrnent for Chiidrm: Summary of Results of Logistic Regession for Predictors Entering the Equation Using Corrected (CA) Scores and Uncorrected Age (UA) Scores

Foundations index Coordination index Nonverbal Index Predictor

CA UA CA UA CA UA

BPD - .O23 ,019 - B irthweight - .O36 .O01 .O01

Brain Lesion .O25 .. .O07 .O20

SGNAGA .O1 1 - - - -

Gender - .O27

# days .O09 ,006 - 002

SES - - GA - - -

TABLE L 1 Miller Assessrnent for Preschoolers Logistic Regression : Percentage Rate of Correct Predicted Classification Usmg Corrected Age (CA) Scores and Uncorrected Age (UA) Scores

Foundations Index Coordination index Nonverbal Index

Median L&GT LT/GT L E ~ T LT/GT L&GT LT/GT L E ~ T LT/GT L&T LTIGT L F ~ T LT/GT

Split 42 42 3 1 31 33 3 3 3 3 3 3 5 3 5 3 30 30

Predicted 71.0 71.2 62.6 68.6 65.0 75.0 65.1 71.0 72.29 80.4 73.5 79.0 Rate

Table 22 M e r Assessment for Preschoolers: Summary of Results of Logistic Regression for Predictors Entering the Equation Using Corrected Age (CA1 Scores

-- - -

p < .O5

Predictor Verbal index Cornplex Tasks index Total Score Index

BPD

Buthweight

Brain Lesion

SGNAGA

Gender

# days

SES

GA

TABLE 23 Milier Assessment for Preschoolers Logistic Regression : Percentage Rate of Corrected Predicted Classification Using Conected .4ge (CA) Scores

Verbal index Cornplex Tasks Index Total Score index

Median Split L E ~ T LT/GT L E ~ T LT/GT L ~ G T LT/W 48 48 50 50 47 17

Predicted Rate 57.0 57.0 71.0 80.4 65.1 65.1

. . . 4.25 Sen- and Specificitv

The sensitMty and specificity of the outcome measures which had the highest

degree of correct classification (greater than 79 percent) were calculated (see

Appendices E & F). SensitMty of the risk index was mterpreted as the proportion of

ELBW children with poorer developmental outcornes who were correctly ciassified by the

nsk index: ie. true positives. The specificity of the risk mdex was defined as the proportion

of ELBW children who were doing well deveiopmentally and were clasdied as such, ie.

true negatives. (Fletcher, Fletcher & Wagner, 1982). (See Table 2 1).

Of the 5 1 ELBW preschoolers classified by logistic regession analysis on the

Nonverbal index - Corrected Age score ushg the method which excluded the scores

falling at the median, 26 feu into the low scoring group. Of these, 2 1 were correctiy

classified by the risk index for a sens i t~ ty of 8 1 percent. (See Appendix E. metcher et

al. 19821). Twenty f i e ELBW preschoolers were above the median for this index Of

these, 20 were correctly classitied for a specîfkity of 80 percent. (See Appendix E,

Ifletcher et al. 19821). Thirty two preschoolers, scoring at the median. were not

classified by definition. (See Appendix I for fiequency distributions). The reason that so

many children scored at the median was a result of the method in which the MAP is

scored, since the range of possible scores is tmcated. For the Nonverbal Index subject

could score at the 3rd. 7tb, 14th , 3ûth, 53rd or 99th percentile scores. Therefore, a

higher proportion of the subjects of average ab* scored at the median than would have

ifthe range of scores was not truncated.

74

Of the 62 ELBW preschoolers classified by logistic regression analysis on the

Nonverbal Index -Uncorrected Age score using the method which excluded the scores

fàlling at the median, 28 were below the median. Of these, 2 1 were conedy classified by

the nSk mdex for a sensitiMty of 78 percent. Thirty four ELBW preschoolers were

above the median for this mdex. Of these, 28 were correctly classified for a specificity of

80% (See Appendix F, metcher et al. 19821). Twenty one preschoolers, scoring at the

median, were not classified by this definition. (See Appendk J for fieequency

distributions).

Of the 5 1 ELBW preschoolers classified by logistic regression analysis on the

Complex Tasks Index-Corrected Age score, 18 were below the median. Of these, 1 I were

correctly classified by the risk index for a senntMty of 78 percent. Thirty three ELBW

preschoolers were above the median for this index. Of these, 30 were correctly classified

for a specifïcity of 8 1% (See Appendk G, metcher et al. 19821). Thirty two

preschoolers, scoring at the median. were not classified by definition. The truncated range

of possible scores for the Complex Task Index included the the 1 st, 4th, 9th , 16th, 3 1 a

50th or 99th percentile scores (See Appendix K for Bequency distributions).

In summary, use of the GTLT way of establishing a median *lit yields a higher

proportion of correctly classified children. However, children who score at the median are

not classified by this method, thereby defeating the goal of classifymg every child in the

sample. This method does ailow children tùnctioning at more extreme points in the

distribution to be classified with greater accuracy by the risk index.

TABLE 23 Sensitivity and Specificity of Risk index for Outcornes Correctiy Clitssified > 799'0 Using Corrected (CA) and Uncorrected Age (UA) Scores

Outcome Corrected/ Sensitivity Specificity Mesure Uncorrected

Age

MAP CA 81% 80% Nonverbal

MAP Nonverbal UA 78% 80%

MAP CA Comp tex Tasks

Chapter V

DISCUSSION

Although this group of children did noi demonstrate major neurological

impairment at the time of assessment, preschool performance as meanired by uncorrected

age was one standard deviation below the mean for published norms in gross and fine

motor performance areas on the PDMS, and ranged fiom the 32nd to the 37th percentiles

on the MAP indicatmg a degree of inrpainnent of preschool skills on these outcome

measures. Differences in outcorne between nursery groups showed lower performance

outcornes for the more medically fiagile infants in the outbom nursery which were still

apparent for the fkst 36 months. UnOre their fùliterm age peers, this group of ELBW

children retained vestigial effects of theû biological fiagility which appeared to be related

to poorer motor and oonverbal skills. Verbal skills and the abüity to combine visual spatial

and motor planning abilities appeared to be relatively well developed m this sample when

compared to age n o m . However, given the lack of uncorrected age scores for both

these indices, these £indmgs remain prelihary at best. The risk index did not classiSr the

results of the Verbal Index weii, nor did any of the predictors enter mto regression

analysis, supportmg the notion that the biological predictors had little to do with verbal

outcomes as previously found by Molfese ( 1989) and Siegel ( 1982). In contrast, while

the Complex Tasks Index seemed to be a relatively well developed skill when CA scores

were used, the risk index predicted the classincation of results into high and low scoring

groups with reasonable accuracy. The sensitivity of the risk index on this outcome was

76

77

such that 1 1 of the 1 8 children scormg below the median were correctly classified as true

posit~es. It remahs to be seen whether, in subsequent assessments which are more

detailed m accordance with age demands, the skik tested m the Cornplex Task Index

would go on to deteriorate because of the unstable auence of the biological risk fàctors

since they were found to be related to both biological and demographic variables

(Binhweight, Brain Lesion and Gender accordhg to logistic regression; GA, SES and

Gender according to stepwise regression). Altematively, as a result of their relation*

to environmental factors, these skills could continue to be an area of relative strength in

the skiu repertoire of this simple,

No single risk predictor contniuted prominently to the variance of preschool

performance outcomes. BPD, Birthweight and Gender contnibuted most eequently

during the aepwise regession analysis. but these variables contniuted difEerently to each

outcome. This hding supports previous literature which found an association of BPD and

Birthweight with poor developmental outcome (Landry et al., 1988), althougb Gender

was associated with fine motor outcomes as well as the ability to perfonn complex tasks,

memory tasks and visual-spatial perception tasks. This may imply that fernale pretenns,

Like their fidl term age peers, are more encouraged to practice this type of skill than boys.

Altematively, the hdings may indicate that the effects of biological immaturity are more

pronounced or sustained in males, particularly m skills which require refinement of h e

motor skill, visud percephial SUS and the ability to combine visual and motor systems to

coqlete complex tasks.

The other predictors fomed different constellations m each of the regression

78

analyses of each of the preschool performance outcornes, and a consistent pattern did not

ernerg e.

Bram Lesion. number of days ventilated, Birthweight and BPD entered into two

or more of the logistic regression analyses. The Birthweight and BPD hdings are

consistent with the r e d t s of the stepwise regreçsion analysis. Logistic regression may

have been more sensitive to Brain Lesion since it is a categorical variable, thereby allowing

it to contrilute more significantly in the analysis.

Both logistic and stepwise regression analyses showed the PDMS-FM to be

associated with Buthweight, Gender and Gestational Age. The Foudations index was

found by both analyses to be associated with BPD. Birthweight and the # days of

ventilation. The Coordination Index was found by both analyses to be associated with

BPD and # days. Both analyses showed that the Nonverbal index was associated with

Binhweight and Gender , the Complex Tasks index was associated with Gender and the

Total Score Index was associated with BPD. Fmally, on both analyses, none of the

variables in the risk index were associated with either the Verbal Index or the PDMS-GM.

The r e d t that noue of the risk index variables were associated with the Verbal

index was interesting in tight of previous hdings. Since the risk index was made up of

several variables which were related to the perinatal conditions of the preterm biRh, the

result may nippon Molfese et al. ( 1993) who suggested that variables unrelated to

biomedical factors have more association with the later development of verbal skills. We

mi@ have expected an association between the Verbal Index and maternai education as

an indicator of SES. However, the absence of this hding may be inconclusive, since only

79

the corrected age scores were available for analytis of the Verbal Index, and few chiIdren

scored in the lower range on this measure.

The lack of significant hdings for the association between the risk index and the

PDMS-GM, when viewed m iight of the significant hdings found for the PDMS-FM and

the MAP Foundations and Coordination Indices, may have been related to the fact that

much of the gross motor repertoire tested by the PDMS-GM is already mature at three.

whereas the motor skills and abilities tested by the other tests are stiU developmg at three.

resulting in a wider range of performance. It may also be that the test items on the

PDMS-FM, Foundations and Coordination Indices are more sensitive to motor

maturational difnculties associated with premahinty than the gross motor skills teaed by

the PDMS-GM. This hding thus contrasts with Mazer et al. ( 1988) who previously

found that motor skills at preschool age were more adversely afEected by low birthweight

than were other domahs of development.

The four performance outcomes which were the moa accurately predicted in the

logistic regession analysis were the Peabody Fine Motor Scales. the Miller Coordination

indeq the Miller Nonverbal Index and the Complex Tasks index . Thus, the skills teaed

by these rneasures appear to be the most sensitive to perinatal difficulties associated with

prematthy. These include motor accuracy for pend control and articulation, s t a c h g a

simple block tower, memory , visual-spatial perception and the abdity to combine visual

and motor abilities m order to complete tasks such as block design, imitation of postures

and motor planning.

The hdmg that each predictor was associated Merently with each of the

80

outcome variables further supports the need for muitivariate anaiysis of risk predictors in

prematurity and subsequent preschool performance. This type of analysis has only been

possible in recent times with the increashg number of ELBW &ors.

It is also noted that the outcome measures m which the risk mdex accounted for

the greatest amount of cumulative variance (MAP Coordination Index MAP Nonverbal

Inde& MAP Complex Tasks index) were oniy measured at moderate levels (see Tables

13 and 14), suggesting that other variables besides the combmation of medical and

environmental variables represented in the Nk mdex may be associated with preschool

perfonnance outcomes. These could mclude early intervention programs as well as other

environmental factors m the home environment.

Clearly, the use of corrected age vernis uncorrected age scores to interpret the

outcomes of the Miller Assessment for Preschoolers was a signifïcant issue in the logistic

analyses. Use of the corrected age scores more accurately identiiïed children not at risk.

Use of the uncorrected age score, however. more accurately predicted the preschoolers

who were at risk for preschool performance. Given previous research (Siegel 1982).

which showed that uncorrected scores were more predictive of school age scores than

were corrected scores, it would be more prudent to use the uncorrected age scores to

detect the possibility of fiiture impairments rather than the corrected age score.

Despte the danger of over identification of the ELBW population at preschool

age, resuits of developmental testing could be interpreted dong a range of corrected and

uncorrected age scores. Following the preschool assessment, parents could be presented

with the range of scores between corrected and uncorrected age perfonnance. in this

way, relative strengths and weaknesses codd be pomted out on the basis of the analysis of

both the scores. Information conveyed in this manner would be more accwate m

descniing the child's status at preschool age, as well as t e h g the parents about a range

of informed possiiilkies for firture outcorne.

Chapter VI

CONCLUSION

6.1 Clinical Relevance of the Study

The contribution of this midy has been to i d e n e that preschool skiils in

the ELBW population who do not demonarate major neurological deficits remam below

age nomis at three years of age. Analysis of preschool performance in motor and

nonverbal domains shows that these skills are poorly developed in this ELBW sample

when compared to standardized n o m . Given the hdings in the Literature, which state

that uncorrected age scores more accurately predict long term outcomes, the use of those

scores to interpret the preschool performance of ELBW preschoolers seems warranted.

The risk index was most effective in the correct classification of preterm preschoolers into

high and low scoring groups on measures of memory, visual-spatial perception and motor

planning. &en the nature of the motor based and nonverbal ditnculties which some of

these children exhibÏted on occupationai therapy assessment, intervention seems

warranted, either through parent education or direct occupational therapy treatment as

individual follow up clinic practices dow. Recent =dies of the efficacy of occupational

therapy programs for motor based and nonverbal problems have been methodologically

weak (Case-Smith, 1996) or oot confined to the preschool ELBW population

( Humphries, Wright, Snider & McDougdI, 1992), however, s igdcant improvements in

rnotor planning ability were found by Humphries et al. ( 1992) when examming the efficacy

83

of this type of occupational therapy m school aged leamhg disabled subjects. It remains to

be seen how effective early mtervention ushg these techniques would be for the ELBW

group. This is an area for fùture research.

The preschool skill areas of memory, visual-spatial perception and motor planning

areas are mostly k e l y to be related to complications associated with prematunty which

are experienced during the early weeks of Me. From this information, we may be able to

identify which ELBW preschoolers are more Likeky to demonstrate the minor neurological

imp airments which may mterfere with the acquisition of early leamhg anà motor skills.

Through appropriate interpretation of these findmgs. we may go on to improve the quality

of Me for both the children and their families.

6.2 Limitations of the Study

The study was limited by the lack of a fU tenu comparison group, although results

were compared to standardized nomis developed for each outcome. Such a comparison

aoup might have mdicated how a local sample compared to the standardized n o m . C,

Because of the nature of the design of the cohon study , and the fact that the data were

iimited to what was available m the medical record, no information was gathered on the

home environment of the children. As a remit, other environmental influences which may

have been associated with the developmental outcome of this cohort of ELBW

preschoolers are not known. Follow up at school age of the subjects fiom this ELBW

sample would have given an additional insight mto the contribution of the Merent

biological and demographic variables at that pomt m development as well as the

relationship between preschool pedomiance skills and school performance skiiis.

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Appendices

Appendir A

Predict ors Correlation Matrix

Brain Lesion

Birthweight

Gestational *4ge

fC Days

BPD

Gender

SES

S GAIAGA

Brain Birthweight Gestational # D- BPD Gender Lesion Age

1-00 0.15 - 0.23 0.18 0.14 0.37

1.00 0.45 - 0.23 - 0.34 - 0.03

1.00 - 0.43 - 0.49 - 0.06

SES

- 0.22

o. O2

- 0.09

- 0.09

- 0.08

- 0.01

1.00

SGNAGA

- 0.32

- 0.37

0.17

- 0.23

-0.14

- 0.01

O. O6

1.00

Appendix B

Predictord Outcome Variables Using Corrected Age (CA) Scores Correlation Matrk

PDMS Gr- Maor

Scaie

PDMS Fine Mdw

S u l e

MAP Formdations

MAP Coordinatxcm

MAP Ncuvatid

M A P Verbd

MAF' Corn plex T*

Appendk C

Predictors/ Outcome Variables Usinp; Uncorrected Age (UA) Scores Correlation Matrix

PDMS Gr= Mda

O. 12 O. 12 0.06 0.03 O. 16 0.02 - 0.04 O. 04

-0.12 0.13 Fmr Mata

O. 14 -0.03 -0.19 -0.17 -0.04 -0.03 s a l e

Appendix D

ûutcome Variables Usbg Corrected Age (CA) Scores Correlation Matrix

PDMS PDMS MAP M A P MAP MAP MAP Gmss FineMoiu Foundatiais Coadkticn Nonverbai V d a l Compirv Maor Suie T& Scde

PDMS G r o s M o t a

WC

PDMS Fmr Muor S d r

Appendix E

Cdculations for SensitMty and Specificity Values for Logistic Regession Outcornes

Correctly Classified at a Rate of > 79%

MAP Nonverbal (CA)

OUTCOME

1 Low l Positive

(+)

Specificity = $ - -

b+d

2 1

True (+)

Negative - )

5

Faise (-)

c

20

Tme (- )

d

Appendix F

Calculations for Sensitivity and Specifidy Values for Logistic Regression Outcornes

Correctly Classified at a Rate of > 79%

MAP Nonverbal (UA)

1 OUTCOME

Positive (+)

Negative (-)

Low

21

True (+) a

6

False (- )

c

27

Higb

7

False (+) b

28

True (-)

d

35

28

34

62

Calculations for SensaMty and Spedicity Values for Logistic Regession Outcornes

Correctly CIas&ed at a Rate of > 79%

MAP Complex Tasks (CA)

1 OUTCOME

Positive

(+'

Negative 6 1

Low

I l

rue (+) a

3

False (-)

c

13

fi&

7

False (+) b

30

Tme (-)

d

37

18

33

5 1

Appendix H

GLOSSARY

Aiveolar septae

Aheoli

Apnea

Aut oregulation

-the tissue mtervening between two adjacent pulmonary alveok consisting of a close-meshed capiilary network covered on both d a c e s by very thin aiveolar epithelial ceus.

-tenninal dilations of the bronchioles of the lungs where gas exchange is thought to occur

-absence of breathmg

-the tendency ofblood to flow toward an organ or part in order to remab at (or renim to) the same levei, despite changes in the pressure m the artery which conveys blood to it. -generally any biologic system equipped with mhibitory feedback W e m s such that a &en change tends to be largely or completely counteracted.

Cavitary necrosis -cavemous hole m brain tissue following brain tissue damage

Corticospinal tract -motor and sensory nerve fibres ninning between the brain cortex and the spmal cord

Cystic -containhg cysts; eg: porencephalic cysts are formed in the brain after brain damage

Haematocnt - blood ceIl count

Homeostasis -the state of equilirium in the body with respect to vanous functions and to the chemical compositions of the fluids and tissues. The process by which such bodily equilibrium is mamt ained.

-subnormal levels of oxygen in air, blood, tissue.

-resulting fiom a defective mechanimi of oxygenation in the lungs caused by abnomial pulmonary fiindon.

Ischaemia

inborn nursery

Intraventricdar

Lateral ventricle

Necrosis

Neurodevelop mental

Outborn nursery

Perinatal

Periventricular

-slower peripheral circulation through tissues, local anaemia as a r e d t of arterial narrowing or mechanical obstruction.

-mtensive care nursery for neonatal care in which the mfants are bom on the maternity ward and transferred within the hospital for special care.

-within the lateral ventncles of the brain

-horseshoe shaped cavity conformIng with the general shape of each cerebral hemiqhere

-pathologie death of one or more ceils, or of a portion of tissue or organ, resulting fiom irreversible damage

-developmental skiil repeitoire relating to neurological maturation

- nursery for neonatal intensive care to which infants born in comrnunity hospital are transported by ambulance or helicopter on an emergency basis to receive special care.

-pertainmg to the periods of tirne before during and after the time of birth

-the area around the lateral ventricle of the brain

Subependymal germinal matrix -ependyma: the cellular membrane lining the central canal of the spinal cord and the brain ventricles -germinal mauix :the cellular structure present at the fetal stage of brain development wbch gives rise to the structure present in the neonate -beneath the ependymal germinal matrk lies a highly vascularized area of the preterm brah anterior to the lateral ventricles. In early periods of gestation, it is subject to bleeding during periods of hypoxia resulting in damage to the surroundmg brain tissues. This damage intefieres with the sensory and motor nerve tracts which pass through the area. (a large portion of these are motor, others are visual) which may lead to impairment m the associated motor and visual systems.

Vasculature -the vascular network of an organ

Ventriculomegaly -enlarged lateral ventricles o f the brain as a result of increase in intercranid pressure fiom a haemorrhage into the ventncles or a mechanical obstruction of the dramage of cerebral spmal fluid.

Appendix 1

Frequency Distribution for MAP Nonverbal Scores (corrected age)

Percentile Score:

3

7

14

30

53

99

Count:

2

4

7

13

32

25

Percent:

2.4 1

4.82

8.43

15.66

38.55

30.12

Appendix J

Frequency Distxiiution for MAP Nonverbal Scores (uncorrected age)

Percentile Score: 1 Count: 1 percent:

Appendix K

Frequency Distribution for MAP Complex Tasks Scores (corrected age score)

Percent: I

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