introduction to growth and development: nutr 526 intrauterine growth and nutrient accretion body...

Introduction to Growth and Development: Nutr 526

Intrauterine growth and nutrient accretion

Body Composition Development

Metabolic Physiologic neurologic

Growth

Fetal Growth from 25-40 weeks GA

Weight increases 4-fold Length and OFC increase 2-fold

Determinants of fetal growth

Genetics Maternal/paternal genes, race, sex

estimated to account for 20% of variance in birth weight

Environmental factors

Body Composition BMI and percentage of body weight

made up of fat increase rapidly during the first months of life Fat accounts for 0.5% of body weight

at the fifth month of fetal growth and 16% at term.

3rd trimester: increase from 1-3% of body weight to 10-16% of body weight at term

After birth, fat accumulates rapidly until approximately 9 months of age

Minerals

Two-thirds of mineral content of full-term newborn is accummulated in the last trimester of pregnancy.

Age-related changes in body composition. (Reprinted by permission ofMosby Year Book. Heird WC, Driscoll JM, Schullinger JN, et al.Intravenous alimentation in pediatric patients. J Pediatr 80:351, 1972.)

Energy Reserves

Birthweight Non protein kcal Total kcal

500 50 225

800 grams 125 435

1000 grams 165 600

1500 425 1120

2000 1050 1975

3500 4175 5924

Environmental factors Maternal health Nutrition

Glucose, fatty acids, amino acids for tissue deposition and fuel for oxidative purposes

Ability of maternal-placental system to transfer nutrients to fetus

Endocrine environment E.g. LGA infant:

glucose-insulin-growth factors

GROWTH IN FIRST 12 MONTHS From birth to 1 year of age, normal human

infants triple their weight and increase their length by 50%.

Growth in the first 4 months of life is the fastest of the whole lifespan - birthweight usually doubles by 4 months

4-8 months is a time of transition to slower growth

By 8 months growth patterns more like those of 2 year old than those of newborn.

Weight Gain in Grams per Day in One Month Increments - Girls

Age 10th

percentile50th

percentile90th

percentileUp to 1month

16 26 36

1-2months

20 29 39

2-3months

14 23 32

4-5months

13 16 20

5-6months

11 14 18

Guo et al., J Peds. 1991

Weight Gain in Grams per Day in One Month Increments - Boys

Age 10th

percentile50th

percentile90th

percentileUp to 1month

18 30 42

1-2months

25 35 46

2-3months

18 26 36

3-4months

16 20 24

4-5months

14 17 21

5-6months

12 15 19

Guo et al., J Peds. 1991

Weight gain of Breast fed vs bottle fedinfants: 8-112 days of age (g/d)

Breast fed Bottle fed

Male 29.8 + 5.8 32.2 + 5.6

Female 26.2 + 5.6 27.5 + 4.9

Nelson et al Early Human Development 19:223 1989

Body Composition BMI and percentage of body weight

made up of fat increase rapidly during the first months of life Fat accounts for 0.5% of body weight

at the fifth month of fetal growth and 16% at term.

After birth, fat accumulates rapidly until approximately 9 months of age

Individual Growth Patterns

Weight and length at term appear to be primarily determined by nongenetic maternal factors

Birth weigh and birth length weakly correlate with subsequent weight and length values

Individual Growth Patterns, cont.

African American males and females are smaller than whites at birth, but they grow more rapidly during the first 2 years

Patterns of growth in breastfed infants are different from formula fed infants

Rates of gain for breastfed and formula fed infants during early months of life generally have been found to be similar although some reports have demonstrated greater gains by breastfed infants and others have shown greater gains by formula fed infants

Growth Assessment

Assessment

Screening identifies nutritional risk Nutrition Assessment

Uses information gathered in screening Adds more in depth, comprehensive

data Interprets data Develops care plan Reassess

Challenges

Information Availability,

sufficiency, accuracy Interpretation

Goals, expectation, “does it make sense”

Questions What are goals and

expectations, “does it make sense”

Growth Concerns

Underweight

Short stature

Overweight

A variety of growth references were developed and and used

in the U.S. since the early 1900’s

Intrauterine/Fetal Standards

Lubchenco Based on birth measurements (weight,

length, OFC) N= 5600 caucasian infants born in

Denver 1948=1961 Does not account for postnatal weight

loss due to fluid adjustments with birth Effect of high altitude

Intrauterine/Fetal Growth Standards

Data Sets: Kramer et al: 676,605 infants 22-43 weeks Nicholson et al : 376,000 Swedish infants

28-40 weeks Breeby et al: OFC (N=29090) and Length

(N=26,973) 22-40 weeks CDC Data

Time period 1963-2001

Postnatal Growth Charts

Accounts for initial weight loss Dancis: Data 1948, very small

sample size in lowest weight group Ehrenkranz: Pediatrics 1999:104:280

N=1660 14-16 g/kg/d weight gain 0.9 cm/week increase length 0.35 cm/week increase OFC

Growth references: timeline Stuart/Meredith

Growth Charts (1946-76)

Caucasian, Boston/Iowa city, small sample size

NCHS growth charts (1976-1978)

NCHS AAP/MCHB study

group Used cross sectional

data from NHES, NHANES, and FELs (infant)

CDC produced normalized version

1978 WHO recommended international use

Growth reference timeline: continued

2000 CDC growth charts: revision of NCHS growth charts

2006 WHO released new international growth standards

Assessment of Growth

Growth Charts CDC/NCHS

http://www.cdc.gov/growthcharts/ World Health Organization

http://www.who.int/childgrowth/en

Specialized growth charts Patterns, rates, velocity

NCHS growth charts: Concerns Infant data: Fels study

Primarily formula fed Underrepresented groups: largely

caucasian, middle class Intervals of measurements (q3

months from 3-36 months) may not define dynamic patterns during rapid growth phases

Statistical smoothing proceedures

CDC Growth charts: 2000

Based on 5 cross sectional nationally representative surveys between 1963 and 1995

Included more breastfed infants

CDC/NCHS Growth Charts

Data from previous NCHS charts came from private study of primarily white, formula-fed, middle-class infants from southwestern Ohio before 1975

Newer charts have more representative data (some breastfeed and ethnic diversity) from NHANES and use more sophisticated smoothing techniques

16 new charts provided by gender and age

CDC Growth Charts (compared to older NCHS

Standardized data collection methods

Expanded sample Exclusions

VLBW infants NHANES III weight data for >6 year

olds

CDC Growth Charts (compared to older NCHS

Standardized data collection methods

Expanded sample Exclusions

VLBW infants NHANES III weight data for >6 year

olds

CDC/NCHS Growth Charts

Clinical charts for infancy for girls and boys: weight length weight for length OFC

Choice between outer limits at 3rd and 97th or 5th and 95th percentiles

Adam

Adam

Carl

WHO Child Growth Standards

Released new growth standards April 2006 Assumed that infants and children

between birth and 5 years grow similarly when needs are met.

Concerns for CDC charts included: Frequency of growth measures during

dynamic periods of infant growth Statistical methods

WHO growth charts

Data from Brazil, Ghana, India, Norway, Oman and USA

Multiethnic, affluent Exclusive breastfeeding to 4 months Solids according to recommendations

6 months Continued breastfeeding to 12 months

WHO growth charts

Full term low birthweight infants not excluded

Birth to 2 years N 1743 ----- 882

2-5 years N 6669

WHO v.s. CDC

Infancy WHO mean > CDC mean birth-6

months “healthy breastfed infants track

weight/age along WHO but falter on CDC”

Cross at 6 months and WHO mean < 6months

WHO v.s. CDC CDC

Heavier, shorter WHO

taller WHO

Higher estimates of overweight Lower estimates of underweight,

undernutrition

Gastrointestinal Maturation

Reference Josef Neu, Gastrointestinal Maturation and

implications for infant feeding, Early Human Development 2007 83 (767-775)

Neonatal Gastroenterology, Clinics in Perinatology June 1996 23:2

Weaver and Lucas Development of Gastrointestinal Structure and Function, Chapter 3 in Neonatal Nutrition and Metabolism ed Hay Mosby 1991

Nutrition and Metabolism of the Micropremie in Clinics in Perinatology March 2000n 27:1

Gastrointestinal Maturation

Intestinal length increase 1000X from 5-40 weeks, doubles in the last 15 weeks.

Villi formed at 16 weeks Fetus begins to swallow around 16

weeks by 2nd trimester is swallowing as frequently as every 45 minutes. By term, the fetus ingests approximately 300 ml/d

Maternal-fetal-placenta Interaction Individual metabolism

Glucose, amino acids, and fatty acids primary nutrients for tissue deposition and oxidative fuel

Hormonal regulation Not well understood Main hormones are placentally produced Insulin like growth factors induce cell proliferation and DNA,

increase glucose and amino acid uptake, and inhibit protein breakdown

Placental growth hormone stimulates IGF and is reduced in IUGR ? Leptin. Associated with fetal weight, fetal BMI, and fetal

fat mass

Carbohydrate Metabolism

Fetus Glucose and lactate

Glucose from maternal circulation via facilitated diffusion At birth, plasma glucose concentration about 2/3 maternal Used for oxidative fuel and source of carbon for glycogen

and other organic compounds Understress fetus can produce glucose with gluconeogenic

enzymes present at 10 weeks (but primarily maintained by maternal supply

hi

CHO

Term Infants: Lactase 30% of adult. Stimulated with

first feeds Preterm infants:

Lactase levels remain low <36 weeks 30-40% NB levels Breath hydrogen tests confirm

inefficient digestion of lactose

CHO

At birth Catoecholamines, thyroxin, and

glucagon increase and falling glucose levels stimulate glu-6-phosphatase

Glycogenolysis and hepatic glucose output are thus stimulated

CHO: Term Infant

Enzyme origin substrate Activity in newborn

amylase Salivary glandsPancreasHuman milk

Starch/glucose polymers

ModerateAbsent<6moshigh

Glucoamylase Intestine Glucose polymers

high

Sucrase-isomaltase

Intestine High

Lactase Intestine Lactose high

GI development Weeks GA

Esophagus Superficial glandsSquamous cells

2028

Stomach Gastric glandsPylorus and fundus defined

1414

Small intestine Crypt and villusLymph nodesPeptides and hormonesNeurotransmittersMyenteric plexus

1414141214

Colon Diameter decreasesVilli disappear

2020

Pancreas Differentiation of exocrine and endocrine tissue

14

Liver Lobule formation 11

Protein

Source of amino acids for protein synthesis

Release of bioactive peptides that contribute to regulation of many physiologic functions including metabolism, immunity, bllod pressure, GI function, and food intake

Protein Metabolism

Fetus requires protein for protein synthesis and the provision of energy

Maternal-fetal amino acid transfer is a complex process involving several sodium dependent transfer proteins. Intracellular and extracellular sodium gradient provides driving force

Fetal amino acid profile differs from neonate

Protein

Digested in upper intestine via pancreatic proteases. Most of the brush border and cytosolic peptidases are well developed in the preterm infant and peptide transport system is efficient.

Macromolucules can be actively taken up by pinocytosis and preterm infants have demonstrated to capability to absorb lactoferrin. Preterm infants have increased intestinal permeability

Lipid Metabolism

Fetus Fetus requires large amounts of lipids

particularly within developing nervous system (DHA, ARA)

Fetus acquires lipid via maternal placental transfer and capable of synthesizing cholesterol and fatty acids

Transfer impacted by maternal FA profile Dependent on maternal supply for EFA

Preterm

Bile acids and lipases limited Approx 30% newborn levels 24-36

weeks

Lipid:Term

Lipase Cofactors Substrate Contribution to fat digestion

Gastric lipase None TG Moderate to high

Pancreas Colipase and bile salts

TG low

Carboxylesterlipase

Bile salts TG Unknown to high

Pancreatic lipase

Phospholipids and TG

unknown

Milk bile salt dependent lipase

Bile salts TG Moderate to high

Development of Infant Feeding Skills Birth

tongue is disproportionately large in comparison with the lower jaw: fills the oral cavity

lower jaw is moved back relative to the upper jaw, which protrudes over the lower by approximately 2 mm.

tongue tip lies between the upper and lower jaws.

"fat pad" in each of the cheeks: serves as prop for the muscles in the cheek, maintaining rigidity of the cheeks during suckling.

feeding pattern described as “suckling”

Developmental Changes Oral cavity enlarges and tongue fills up less Tongue grows differentially at the tip and

attains motility in the larger oral cavity. Elongated tongue can be protruded to receive

and pass solids between the gum pads and erupting teeth for mastication.

Mature feeding is characterized by separate

movements of the lip, tongue, and gum pads or teeth

Development Neurophysiologic

Homeostasis Attachment Separation and

individuation Oral Motor

Stages of Development

Homeostasis Attachment Separation and individuation

StagesAge Development

1-3 months

Homeostasis * State regulation* Neurophysiologic stability

2-6 months

Attachment * “falling in love”* Affective engagement and interaction

6-36 months

Separation and individuation

* Differentiation* Behavioral organization and control

Feeding behavior of infants Gessell A, Ilg FL

Age Reflexes Oral, Fine, Gross Motor Development1-3months

Rooting and suckand swallowreflexes arepresent at birth

Head control is poorSecures milk with suckling pattern, the tongue projectingduring a swallowBy the end of the third month, head control is developed

4-6months

Rooting reflexfadesBite reflex fades

Changes from a suckling pattern to a mature suck withliquidsSucking strength increasesMunching pattern beginsGrasps with a palmer graspGrasps, brings objects to mouth and bites them

7-9months

Gag reflex is lessstrong as chewingof solids beginsand normal gag isdevelopingChoking reflexcan be inhibited

Munching movements begin when solid foods are eatenRotary chewing beginsSits aloneHas power of voluntary release and resecuralHolds bottle aloneDevelops an inferior pincer grasp

10-12months

Bites nipples, spoons, and crunchy foodsGrasps bottle and foods and brings them to the mouthCan drink from a cup that is heldTongue is used to lick food morsels off the lower lipFinger feeds with a refined pincer grasp

How?

Establish healthy feeding relationship Recognize child’s developmental abilities Balance child’s need for assistance with

encouragement of self feeding Allow the child to initiate and guide

feeding interactions Respond early and appropriately to

hunger and satiety cues

Analytical framework for the Start Healthy Guidelines for Complementary foods (JADA, 2004)

Baby Zoe

At BirthMaternal-Infant

DyadBreastfeeding Who does what?ExpectationsSubsequent feeding

practices?