thalassaemia trait and pregnancy · pregnancy the critical point or value to distinguish between...

J Clin Pathol 1985;38:810-817

Thalassaemia trait and pregnancy

JM WHITE, R RICHARDS, M BYRNE, T BUCHANAN, YS WHITE, G JELENSKI

From the Department ofHaematology, Corniche Hospital, Abu Dhabi, United Arab Emirates

SUMMARY The haematological variables, haematinic state, and placental function of more than2000 pregnant women, heterozygous for either a- or f3-thalassaemia genes, were examinedduring pregnancy. Four features emerged. Firstly, it was possible by discriminant functionanalysis of haematological variables to distinguish in pregnant patients between the anaemiacaused by thalassaemia trait and that caused by iron deficiency. Secondly, patients with thalas-saemia become significantly more anaemic in pregnancy, ,8 more than a, but this was mainly dueto plasma dilution. From the data percentile curves were drawn for each type of thalassaemiawhich predicted the patients' expected "normal" haemoglobin throughout gestation. Thirdly,patients with a-thalassaemia had the same incidence of iron deficiency as normal pregnantpatients, whereas in those with f8-thalassaemia it was four times less common. The incidence offolic acid and vitamin B12 deficiency was the same in all groups. Finally, as assessed by serum

oestriol concentration, there did not appear to be any abnormality of placental function or fetaldevelopment associated with maternal thalassaemia, and, also, there seemed to be no increase inmaternal or fetal morbidity in pregnancy.

Adult male or female carriers of either a- or,B-thalassaemia trait are not usually seriouslyanaemic, although there is some variation betweenethnic groups, sexes, and individual patients.' Theanaemia usually worsens at times of clinical stress,notably infection and commonly (or always) preg-nancy. Indeed, female patients may present or bediagnosed for the first time in pregnancy as cases ofrefractory hypochromic anaemia.

Despite thalassaemia trait being the most com-mon maternal genetic abnormality associated withpregnancy, there is still uncertainty regarding theclinical course, complications, and management,probably because there are few well reportedstudies.2 For example, it is uncertain, because ofplasma dilution, whether or not thalassaemia traitcan be suspected in pregnancy from an examinationof the haematological variables. Also there are fewdata regarding the pathogenesis of the increasedanaemia or the need for iron and folate supplemen-tation. Finally, and most importantly, there is noevidence as to whether or not maternal thalassaemiais associated with an increase in fetal or maternalmorbidity.To investigate these problems we studied 2326

pregnant patients heterozygous for eithera-thalassaemia (90%) or for ,/-thalassaemia (10%)

Accepted for publication 25 March 1985

and compared our findings with those of 7000pregnant normal subjects.

Patients and methods

PATIENTSPregnant women of 16 different ethnic origins tem-porarily resident in the United Arab Emirates werestudied: 46% were from the Middle East, 14% fromnorth Africa, 35% from the Indian subcontinent,and 3% from other countries. Two per cent of thepopulation was Caucasian.

Data were collected over 18 months and com-puted on more than 9619 pregnancies. Mostpatients (80%) were normal, but the remainderwere carriers of either a- (18%) or ,8- (2%) thalas-saemia genes.

Thalassaemia stateEarlier findings3 had indicated that the a- and,f-thalassaemia trait was extremely common amongthe populations studied. The diagnosis was based onthe association of hypochromia, microcytosis, a rela-tive erythrocytosis, and a normal serum ferritin con-centration. 13-thalassaemia trait was confirmed byfinding a raised Hb A2 concentration anda-thalassaemia by the association of the abovehaematological variables and normal serum ferritinand Hb A2 values.' Although different molecular

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types of a- and ,B-thalassaemia genes must be opera-tive, it is useful clinically to divide carriers into threemain groups depending on their mean corpuscularhaemoglobin contents, which is an index as to thetype and severity of the genetic defect (Table 1).Table 2 shows the type and proportion of thalas-saemia carriers in each group.

Iron deficient subjectsTwo hundred and fourteen patients had pure irondeficiency anaemia, which was suspected onhaematological grounds and confirmed by findingserum ferritin concentrations of less than 10 ng/ml.All responded to oral iron treatment, and afterabout eight weeks the mean corpuscular haemoglo-bin content had risen to more than 27 pg. Thehaematological variables of these patients at presen-tation were compared with those of patients withthalassaemia.

METHODSThe routine performance of the haematologylaboratory is continuously monitored by the UnitedKingdom national external quality assessmentscheme; in 1983 and 1984 the overall assessmentindex was 0 5 (good).

Haematological indices were measured on routineedetic acid blood samples using a Coulter Model S,calibrated with Coulter Counter cell control 4C. Thedata were stored in a computer (Commodore PETII).Haemoglobin A2 concentrations were measured

by DE chromatography at pH 8-4. The normalrange for the laboratory was 2-8 0 05%, and val-ues above 4 0% were considered diagnostic of,8-thalassaemia trait.' Serum ferritin concentrationwas measured using the radioimmunoassay kit(Amersham). In this laboratory values of less than

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10 ng/ml had been established as indicative of irondeficiency.3 Serum folate and vitamin B,2 concentra-tions were measured by a radioimmunoassay doubleantibody technique (Amersham) using quoted val-ues as the normal range. The total serum oestriolconcentration was also measured by a radioim-munoassay double antibody technique (Amersham).

Collection of dataMost patients were studied throughout pregnancy,during labour, and after birth. Data were derivedfrom patients receiving accepted normal antenatalcare with iron and folic acid supplementation, andno attempt was made to select out the patients withthalassaemia and ensure that the iron and folateconcentrations etc were normal. Instead, the overallchanges of the haematological variables were moni-tored as if for normal pregnant mothers. To assesshaematinic requirements ferritin, folate, and vitaminB12 concentrations were determined on about 1000subjects on initial examination (normal subjects andthalassemia carriers) and again at 36 weeks or later.Fetal development was assessed retrospectively byexamining the total serum oestriol concentrations,which had been measured between 28 weeks andterm, in over 300 patients who proved subsequentlyto have thalassaemia.

Results

DIAGNOSIS OF THALASSAEMIA IN PREGNANCYTo determine whether it was possible to distinguishin pregnancy between hypochromic anaemia due tothalassaemia and that due to iron deficiency the dis-criminant function index of England and Fraser5 wascalculated from the patients' variables using theformula:

MCV-RBC-(5 x Hb) - 3-4

Table 1 Grouping ofpatients into three types based on mean corpuscular haemoglobin content

Mean corpuscular haemoglobin Thalassaemia type Probable defectcontent (pg)

Grade 1 27-25 a2_-thalassaemia One a gene deletedGrade II 24-23 a'-thalassaemia One a gene deletedGrade III 22-18 /3-thalassaemia One A3 gene deleted

Table 2 I-ncidence and type ofthalassaemia in the patients studied*

Mean corpuscular Grade ofhypochromia Totalhaemoglobin content(pg) 1 11 111

27-25 24-23 22-18

Number of patients (%) 1759 (18) 808 (8.4) 208 (2.2) 2775 (28.6)% with a-thalassaemia 100 88 74% with ,3-thalassaemia - 12 26

'Total number of patients studied = 9619.


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where MCV = mean corpuscular volume, RBC =red blood cell count, and Hb = haemoglobin con-centration. Fig. 1 shows the data as composite his-tograms. These compare the discriminant functionsof thalassaemic patients with mean corpuscularhaemoglobin contents of 19-22 pg and 23-24 pgwith those of subjects with proved iron deficiencyassociated with the same degree of hypochromia at20 and 40 weeks' gestation. For patients with severehypochromia (19-22 pg) the function for patientswith thalassaemia was -10 to + 15, whereas that ofiron deficient patients was + 15 to +30. There was asmall overlap of the functions of about 4-0% at lessthan 20 weeks, which increased to 7% at 36 weeksor more. For patients with mean corpuscularhaemoglobin values of 23-24 pg the degree of over-lap was slightly greater: 6*0% at less than 20 weeks

Mecnr) corFusC

10

+10 -

+20 7

+30

a

10-

0-

+10

+20 -

+30 -

ulcr hoemoglobin 19-22pg

I--T-----1--1'I I11-

Mean corpuscular haemoglobin 23-24 pg

-t~~~~~~~~~~~~~~~~-

-_ -r _r--_-T 1.0 5 10 15 20 25 30 35 5 10 15 20 25 30 35

< 20 weeks > 36 weeks

Fig. 1 Comparison between the discriminant functions ofpregnant patients with a- and 3-thalassaemia trait (meancorpuscular haemoglobin content 19-22 pg and 23-24 pg)(unshaded) with those ofpregnant patients with pureuntreated iron deficiency anaemia (shaded) with the samedegree ofhypochromia. The discriminant functons ofpatients with thalassaemia fall between -10 and +15 whilethose associated with iron deficiency fall between +15 and+30. For hypochromia of19-22 pg the overlap is 3-7 and6 5% respectively, whereas for hypochromia of23-24 pg itis S-6 and 13*4%.

White, Richards, Byrne, Buchanan, White, Jelenski

rising to 14% at more than 36 weeks. With a meancorpuscular haemoglobin content of 25 pg andabove the separation was less clear and the use ofthe function became unreliable (data on request). Inpregnancy the critical point or value to distinguishbetween the function associated with thalassaemiaand that of iron deficiency was + 15, which is strik-ingly different from the value of 0 found in thenon-pregnant state.5 This variance results from therelative lowering of the absolute erythrocyte countin pregnancy due to expansion of the plasma vol-ume.

HAEMATOLOGICAL VARIABLES DURINGPREGNANCYFig. 2 shows the variation in the mean haemoglobinconcentration during pregnancy in normal subjectsand in patients with thalassaemia and Table 3 showsthe mean variation of all haematological vari-ables. Although the haemoglobin concentrationsin patients with thalassaemia are considerably lowerthan those of normal subjects when values areexpressed as a ratio of the haemoglobin concentra-tion at less than 20 weeks' gestation, the net changeis the same in all four groups. This indicates that theincreased anaemia is due mainly to expansion of theplasma volume with little in the way of increasedhaemolysis. The finding that the absolute reticulo-cyte counts of normal and thalassaemic patientsshowed no significant variation during gestationsupports this conclusion. (Table 4).

Fig. 3 shows the haemoglobin concentrations ofthe four groups expressed as percentile curves. Theranges of values in each group varied considerably,but the degree of variation-that is, the limits be-tween the 10th and 90th percentiles-is roughly ofthe same magnitude for each group during gestation.The value of these curves in practice is illustrated bythe following case history:

Case History: A 26 year old Scottish girl presentedat the hospital in December 1983. Results ofbiochemical investigations were as follows: haemo-globin concentration 12-7 g/dl with mean corpuscu-lar haemoglobin content of 24 pg and red cell countof 4-9 x 1012/1. The Hb A2 concentration was nor-mal at 2-7%, and the ferritin concentration wasnormal at 23*8 ng/100 ml. A diagnosis ofa-thalassaemia was suspected and this wasconfirmed by finding an c:,8 ratio of 0-72:1. Shebecame pregnant, and in March 1984 presented forantenatal care at 18 weeks' gestation. Her haemo-globin concentration was 11-4 g/dl with the othervariables unchanged; this is just below the 50th per-centile for her a-thalassaemia. She was given ironand folic acid and was not seen again until she was

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Non-pregnant

14,Pregnancy Postnatal

Mean corpusculair013 hNoof patents hoemoglobin (pg)cb- -*4-------- 2142 28+ (normal)

'I \ ° *.__. 624 25- 27

ill ...\-Ul \ *~ ' L431 23 - 24

%%M

. I

9- _ 19 - 210~~~~~~04

20 30 loGestation (wk)

Fig. 2 Comparison ofthe variation ofthe mean haemoglobin concentrations ofpregnant patients with thalassaemia traitwith those ofnormal pregnant patients throughout gestation. Only mean values are shown and for clarity the ranges havebeen omitted, but for each grade ofhypochromia the differences are highly significant at each gestational age. The threegrades ofhypochromia loosely represent the severity ofthe thalassaemia. The progression ofthese haemoglobin values doesnot represent individual patients, but the mean ofthe group.

Table 3 Variations in mean or red cell indices with Gestational stage in normal subjects and patients with thalassaemia(grade 1-111)

Haemoglobin Ratio of haemoglobin Red blood cell count Mean copuscular volumeconcentration (gidl) concentration: value at (xl10/l) (fl)

at <20 wk

Normal subjects(MCH 28 + pg(n = 6844))

20 wk 12-69 1-0 4-245 86-5020-24 wk 11-79 0-93 3-911 88-2125-26 wk 11-67 0-91 3-842 89-2531-34 wk 12-04 0-94 3-954 88-8335-40 wk 12-43 0-97 4-118 88-58Grade IMCH 25-27 pg (n = 1759))

20wk 12-27 1-0 4544 80-5620-24 wk 11-46 0-93 4-261 80-5425-26wk 11-21 0-91 4-177 80-9427-30 wk 11-23 0-92 4-167 81-1031-34 wk 11-41 0-93 4-223 81-1135-40 wk 11-51 0-93 4-288 81-00Grade 11(MCH 23-24 pg (n = 808))

20 wk 11-36 1-0 4-830 71-6520-24 wk 10-43 0-91 4-449 71-5525-26 wk 10-31 0-90 4-368 71-8927-30 wk 10-45 0-92 4-403 73-0531-34 wk 10-31 0-90 4-389 72-2835-40 wk 10-58 0-93 4-510 72-72Grade III(MCH 18-22 pg (n= 208))

20 wk 10-63 1.0 5-090 65-1720-24 wk 9-779 0-92 4-692 65-4925-26 wk 10-05 0-92 4-751 66-3127-30 wk 9-422 0-94 4-464 66-6531-34 wk 9-837 0-88 4-694 65-8835-40 wk 10-17 0-96 4-801 66-56

MCH = mean corpuscular haemoglobin content.

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Table 4 Mean absolute reticulocyte counts (Xix'2idl) ofnormal subjects and patients with thalassaemia (grade I1, meancorpuscular haemoglobin content 18-22 pg) during gestation

Gestation (wk)

20-24 25-26 27-30 31-34 35-40

Normal subjects (n = 426) 0(85 0(73 0(71 0(8 0(9Patients with thalassaemia

(n = 331) 0(87 0(76 0(73 0(84 0(93p 0-1 0(1 0(2 0(1 0(15

151

14]

13-

12 -

11 -

Mean corpuscular haemoglobin 28* (pg)

v% ---5901~~~~~~~~~0% ___

2910C'0acr9

8-

_c . . . . . .c 15 Mean corpuscular haernoglobin 23- 24 (pg)c.0 14L0

Ei3212-

11-

10-

9._

8

5010

I~1~ I I I I I I I I

22 24 26 28 30 32 34 36 38 40Gestation (wk)

Mean corpuscular haemoglobin 25-27 (pg)

'-

90

50

" ---- 10

I I I I I I I I I

Mean corpuscular haemoglobin 18- 22 (pg)

50_--,-10

I I I I I ! I I I I

22 24 26 28 30 32 34 36 38 40

Fig. 3 Percentile curves ofhaemoglobin concentrations ofnormal pregnant women and pregnant patients withthalassaemia (grade I-III) during gestation. Curves were drawn from the data ofmeasured values for each group. Patientswere not selected, but were receiving normal antenatal care. In practice, we found that haemoglobin values falling below the10% percentile were usually associated with a secondary cause-for example, urinary tract infection or iron deficiency. Anillustration ofthe value ofsuch normograms is depicted by the case history described in the text.

was 30 weeks' pregnant. Her haemoglobin concent-ration had fallen to 9-0 g/dl at the 10th percentile forher a-thalassaemia. The mean corpuscular haemog-lobin content was unchanged but she admitted nottaking iron. Her ferritin concentration was reducedto 3-1 ng/100 ml. She was given intramuscular ironand in six weeks the haemoglobin concentration had

risen to 11 g/dl, at her original 50th percentile point.Therefore, although anaemic, the haemoglobin wasnow normal for her thalassaemic state. She has sincedelivered a healthy baby boy without any complica-tions.Of interest is the pattern of haemoglobin variation

during gestation associated with thalassaemia. The

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haemoglobin concentration decreased less as thegrade of thalassaemia became more severe. Forexample, in the 23-24 pg group the decrease at25-26 weeks (mean change in haemoglobin con-centration -0-8 0-5 g/dl) was less than that in thenormal subjects (-11 + 0-99 g/dl); in the 19-22 pggroup the haemoglobin value increased: (meanchange +0-3 0-12 g/dl). The same change in pat-tern is seen in the red blood cell count (Table 3).

HAEMATINIC STATETable 5 shows the changes in the ferritin concentra-tions during pregnancy in normal subjects andpatients with a- and f3-thalassaemia. At term theincidence of iron deficiency in patients witha-thalassaemia is the same as that of normal sub-jects, but in those with /8-thalassaemia it is fourtimes less common, occurring in no more than 4% ofpatients. In some patients with thalassaemia andsevere iron deficiency (serum ferritin 5 ng/ml) thediscriminant function, as expected, fell into the criti-cal area. There was no precise correlation, but ifpatients were over deficient there was usually a fallin the mean corpuscular haemoglobin content below28 pg.Serum folate concentrations at less than 20 weeks'

gestation showed no difference between the normalsubjects and patients with thalassaemia (a or 8)(Table 6), and by term, although the degree of defi-ciency was high (11%), it was the same for eachgroup. Similarly, there was no difference in theoverall vitamin 1,2 concentrations and incidence ofdeficiency between normal subjects and patientswith thalassaemia (Table 6).

PLACENTAL FUNCTIONThe total plasma oestriol values of 325 patients with

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/3- or a-thalassaemia are shown in Fig. 4, where theyare compared with our own normal non-thalassaemic range. No difference was found be-tween the two groups. This was a retrospectivestudy-in other words, the values were obtainedfrom the records of patients who were subsequentlyshown to be thalassaemia carriers.

Discussion

We believe that this report represents the largeststudy of the variation of the haematological state,the haematinic requirements, and the placentalfunction in pregnancy of patients with thalassaemia.Although the patients studied originated from theMiddle East, north Africa, and Indian subcontinent,it is probably correct to assume that the clinicalexpression of the types of thalassaemia seen are

comparable with the clinical expression of the dif-ferent types of molecular a- and /8-thalassaemiaseen in Mediterranean and Far Eastern people.

Several points have emerged. Firstly, it is possibleto distinguish with a high degree of certainty bet-ween the hypochromia caused by a- and/3-thalassaemia and that caused by pure iron defi-ciency anaemia in pregnancy. Patients with thalas-saemia have consistently increased red cell countscompared with iron deficient pregnant patientsdespite expansion of plasma volume. Although thediscriminant function index is only a guide to thecause of the hypochromia, it does provide a rapidsimple indicator as to the need for further investiga-tion. Moreover, as we have not found any significantdecrease in the Hb A2 concentration due to frankiron deficiency anaemia (normal subjects 2-8 g/dl +

0-05%; iron deficiency 2-75 g/dl + 0.06%), and notsurprisingly, during gestation, it should be possible

Table 5 Serum ferritin concentrations (nglml) ofnormal subjects and patients with thalassaemia

Gestational Normal (n = 726) fS-thalassaemia (n = 71) a-thalassaemia (n = 526)stage

Mean Range Deflicient* Mean Range Deficient Mean Range Deficient(%o) ( So) ( So)

20 wk 29-7 16-79-6 (6-3) 36-8 1-130 (2-1) 31-3 0-5-79 (5-6)36+ wk 20-4 0-63-1 (22-4) 31-2 3- 89 (4.1) 22-3 16-63 (17.4)* Deficient = ferritin concentration <10 ng/ml.

Table 6 Serum folate and vitamin B12 concentrations in norm4l subjects and in patients with thalassaemia

Gestational Normal (n = 784) (3-thalassaemia (n = 97) o-thalassaemia (n = 214)stage (wk)

Mean Range Deficient* Mean Range Deficient Mean Range Deficient(So) (to) (%)

Folate concentration (/Ag/1) 20 3-6 0-7-15-5 (9-2) 3-1 0-4-12-1 (8.3) 3-3 0-3-13-1 (7.2)36+ 2-9 05-12-1 (11-2 3-2 06-14-1 (10-7 3-1 0-2-11-6 (10-1

Vitamin B2 concentration (ng/l) 20 276 52-794 (7.8) 296 43-1100 (6.7 278 27-760 (6.3)36+ 231 30-562 (37-6) 228 32-761 (33.4) 237 31-9-61 (32-0)

*Folate deficiency <2-0 Agll; B2 deficiency <150 ng/l.


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1400

1200

- 10000EC

. 800

c 6005

.o'am 400

200

0

* Level*MeanU

_~~-- U * 3 U

U -0 Ui29 30 31 32 33- 3ig 30 31 32 33 34 35

Gestation (wk36 37 38 39 L0 41

I)Fig. 4 Totalplasma oestriol concentrations in 325 pregnant patients with a- or /3-thalassaemia traitgrade III (meancorpuscular haemoglobin content 18-22 pg). The upper and lower normal values are shown as the continuous line.In all but four patients the reason for measuring the oestriol concentration was for suspected placental or fetalabnormality, not for anaemia. The data were obtainedfrom records ofpatients with mean corpuscular haemoglobincontents of18-22 pg at the time when the oestriol was measured; the diagnosis ofthalassaemia was establishedsubsequently.

to diagnose /3-thalassaemia conclusively anda-thalassaemia by exclusion. We have ignored thelikelihood that some of the patients considered ashaving a-thalassaemia might have 8,3 thalassaemia,but the incidence is likely to be low and also theprecise type of thalassaemia is not clinically impor-tant in this study.The increased anaemia associated with thalas-

saemia carriers depends on the severity of thethalassaemia, a guideline to which is the mean cor-puscular haemoglobin content at presentation, butduring gestation it is largely due to an increase in theplasma volume. There is no evidence for increasedhaemolysis. We found, however, that as the expres-sion of the type of the thalassaemia becameworse-that is, the mean corpuscular haemoglobincontent decreased-the pattern of haemoglobinchange was quite different and was associated withan increase in the haemoglobin concentration ataround 28 weeks. This could be due to an increasedproduction of red cells at this time or, alternatively,due to a smaller change in the plasma volume.Although the latter hypothesis is difficult to prove, itis attractive and may be determined by the control

of the intravascular fluid volume department, whichis influenced by the osmotic control of the totalintracellular haemoglobin content.The percentile curves showing the haemoglobin

concentrations for each grade of thalassaemia dur-ing gestation have proved to be of practical value.For example, the mean haemoglobin concentrationfor any particular type of thalassaemia at presenta-tion should be accepted as the norm for that patientprovided there is no other complication. Thereafter,it should remain at or near the same percentilethroughout gestation, and any decrease will be dueto a secondary factor-for example, iron deficiencyor infection.The studies on the haematinic state have shown

that there are no differences in the degree of defi-ciency of serum folate or serum B,2 between patientswith thalassaemia and normal subjects, and withregard to folic acid normal supplementation wouldappear adequate. It is worthwile emphasising thatthe observed and often severe laboratory folate orB12 deficiency may go unsuspected because of thelack of macrocytosis of erythrocytes or hyperseg-mentation of neutrophils. The lack of macrocytosis

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may be due to restriction of red cell size in patientswith thalassaemia; the hypersegmentation of neut-rophils is unexplained. As others have found, how-ever, there is a dichotomy between the in vitro val-ues and the in vivo evidence for megaloblastosis inpregnancy.6 The remarkably high incidence of vita-min B12 deficiency found in our subjects is probablydue to ethnic or dietary variations.The reason for the differences in the iron states of

patients with a- and ,8-thalassaemia is not yet clear.it is thought that f3-thalassaemia is associated morewith dyserythropoiesis than a-thalassaemia, thusproviding a greater stimulus for iron absorption.Results of preliminary studies, however, in whichserum a-hydroxybutyrate dehydrogenase, an indexof dyserythropoiesis, has been measured in patientswith a- and j8-thalassaemia with severe hypo-chromia (mean corpuscular haemoglobin content19-21 pg), show no significant difference (White etal, unpublished observations). Although it appearsthat patients with /8-thalassaemia are "protected"from developing iron deficiency, it does occur and itwould seem sensible to supplement the 1 g of ironrequired for each pregnancy. It is also noteworthythat none of the f3-thalassaemia carriers were ironoverloaded.

Finally, the most important observation is thatmaternal thalassaemia, as assessed from the oestriolvalues, does not appear to have any effect on placen-tal function of fetal development. Moreover, therewas no increase in maternal morbidity-that is, ratesof caesarian section, pre-eclampsia and so on.

In summary, the results of this study suggest that

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maternal thalassaemia per se should not give rise toconcern and patients should receive normalantenatal care with no active intervention toincrease the haemoglobin concentration so long as itremains within the normal expected value for thattype of thalassaemia. Once thalassaemia has beendiagnosed in pregnancy, then it is assumed thatgenetic counselling of the parents would take place.

We thank the doctors of the Department of Obstet-rics and Gynaecology at the Corniche Hospital andall the nursing staff for their cooperation in thisstudy.

References

Weatherall DJ, Clegg JB. The thalassaemia syndromes. 3rd ed.Oxford: Blackwell Scientific Publications, 1980.

2 Knox-Macauley HHM, Weatherall DJ, Clegg JB, Pembrey ME.Thalassaemia in the British. Br Med J 1973;iii: 150.

3 White JM, Richards R, Buchanan T, Byrne M, White YS,Sheik-Yousouf IS, Frost B. Thalassaemia genes in PeninsularArabs. Br J Haematol (in press).

Efremov GD. An evolution of the methods for quantitation ofhemoglobin A2. Results from a survey of 10,063 cases.Hemoglobin 1977;2:197.

England JM, Fraser PM. Differentiation of iron deficiency fromthalassaemia trait by routine blood count. Lancet 1973;i:449.

6 Chanarin I. The megaloblasic anaemias. 2nd ed. Oxford: Black-well Scientific Publications, 1979.

Requests for reprints to: Professor JM White, MedicalDirector, El Seif/AMG Joint Venture, PO box 25639,Riyadh 11461, Kingdom of Saudi Arabia.


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