J. clin. Path., 29, Suppl. (Roy. Coll. Path.), 10, 42-53

Haemoglobinopathies in pregnancy

R. G. HUNTSMAN

From the Memorial University of Newfoundland, St John's, Newfoundland, Canada

The haemoglobinopathies are a heterogenous groupof disorders which have highly variable clinicalmanifestations. At one end of the spectrum there isincompatibility with life and, at the other end, thepatient under a stress, such as pregnancy, mayexperience some deterioration in her normal healthystate. Outside this wide range lie the symptomless car-rier states which may demand obstetric action onlybecause of problems connected with genetic counsel-ling or antenatal diagnosis.

It must be instantly apparent that the possiblepathology to be expected during the pregnant statewill vary from one clearly defined genetic entity toanother. On top of this, even within one clearlydefined disease process, eg, sickle-cell anaemia, thereare widely varying degrees of clinical severity. Somewomen with sickle-cell anaemia appear to have childafter child effortlessly, whilst others are racked withcrisis after crisis during their first pregnancy until, atsome point (often around the time of delivery), theyeventually succumb. Some of the extenuating factorsare becoming understood but in many cases the dif-ferent clinical course run by the same genetic diseaseis quite inexplicable.An understanding of the underlying pathology-

which leads on to an attempt to rationalize obstetricmanagement-depends upon a basic knowledge ofprotein structure and simple Mendelian genetics.Once these are understood, the classification of thehaemoglobinopathies is easily comprehended.

In the haemoglobinopathies, the anaemia is due tolack of the normal protein globin, which is an essen-tial part of the haemoglobin molecule, and the redcells produced have a shortened life span, causing achronic haemolytic anaemia.

This lack of normal globin may be due to either:(1) the manufacture within the developing red cell ofan abnormal globin which, when combined withhaem, results in an abnormal haemoglobin; (2)failure of the developing red cell to produce enoughglobin (thalassaemia). In this case, the affected geneproduces either an inadequate amount of globin orno globin at all.Both the abnormal haemoglobins and the thalas-

saemias give rise to health problems of immense

proportions. The World Health Organization esti-mate that each year 80000 children die (mainly incentral Africa) of sickle-cell anaemia and 100000children die of ,B thalassaemia major. Whilst /thalassaemia major remains a lethal childhooddisease, better medical care now permits manypatients with sickle-cell anaemia to live long enoughto become pregnant and conceive children. Becauseof large-scale immigration, many doctors in theUnited Kingdom now have first-hand experience ofboth these disorders and it is with sickle-cell haemo-globin and 3 thalassaemia that this article is mainlyconcerned.

The Structure of Haemoglobin

The haemoglobins are a group of related proteins(globins) to each of which the same prosthetic grouphaem (an iron-porphyrin complex) is attached. Thefunction of the globin is to make the haem solubleand at the same time to prevent its ferrous iron atomfrom becoming permanently oxidized to the ferricform, which cannot combine with a molecule ofoxygen.There are 20 structurally different types of amino-

acids. Globin contains a total of about 150 of them,the 20 different varieties being linked together bypeptide bonds to form a polypeptide chain. Theexact aminoacid occupying each of the sites of apolypeptide chain is predetermined by the DNA ofthe structural gene responsible for its manufacture.

There are three important normally occurringhuman haemoglobins. These haemoglobins differfrom each other because they are constructed fromdifferent polypeptide chains, which have been giventhe letters of the Greek alphabet oX (alpha), / (beta), y(gamma) and 8 (delta). For example, all normalhuman a chains are similar to each other but theydiffer from the /3, y and 8 chains because the amino-acids are arranged in a different order. Similarly thenormal human /3, y and 8 chains all have their ownspecific aminoacid sequence determined by their ownstructural genes. Other haemoglobins have beendescribed containing E (epsilon) and 4 (zeta) chainsbut they are not of practical importance.

42

Haemoglobinopathies in pregnancy

1 ADULT HAEMOGLOBIN (HAEMOGLOBIN A)This is the normal haemoglobin of the adult com-prising about 98 per cent of the total. Two pairs ofpolypeptide chains make up each completed mole-cule. One pair is made of two cx polypeptide chainsand the other pair of two fi chains.

Adult haemoglobin = 0x2 P2w611-

2 FETAL HAEMOGLOBINA baby is born with about 70 per cent of fetalhaemoglobin and 30 per cent of adult haemoglobin.The fetal haemoglobin is virtually all replaced byadult haemoglobin in the first year of life, dropping toa level of under 2 per cent of the total haemoglobinpresent in the adult. Fetal haemoglobin has a pair ofy chains instead of the 8 chains of adult haemoglobin.

Fetal haemoglobin = cx2 2FI

It is usual to find a raised level of fetal haemoglo-bin in adults with sickle-cell disease and haemoglo-bins C, D and E disease. The carriers ofhaemoglobinS, C, D or E do not have raised levels of fetalhaemoglobin.

Patients with fi thalassaemia major have a raisedpercentage of fetal haemoglobin. Fetal haemoglobinis elevated in about half the carriers of ,B thalas-saemia (8 thalassaemia minor).Some individuals fail to switch off their fetal

haemoglobin production during their first few monthsof life. This condition (hereditary persistence of fetalhaemoglobin) is unassociated with disease and is oftheoretical rather than practical importance. It must,however, be admitted that pregnancy in a womanwith 100 per cent of fetal haemoglobin in her redcells would provide a fascinating study of oxygentransport across the placenta. Such a situation hasyet to be described in a woman in the pregnantstate.

In late pregnancy small quantities of fetal haemo-globin may be produced by normal mothers (Pembreyand Weatherall, 1971), suggesting a hormonalreactivation of the now dormant y polypeptidechain gene, a reactivation which sometimes occurs insome unrelated haematological disorders such asleukaemia.

3 HAEMOGLOBIN A2This is present in the normal adult at a level of about2 per cent. Haemoglobin A2 has a pair of 8 chainslinking with a pair of of chains.

43

Haemoglobin A2 = CX2 82 dOL 61oT7

IL I

Raised levels of haemoglobin A2 are found in thegreat majority of the carriers of ,B thalassaemia.

Inheritance

THE INHERITANCE OF SICKLE-CELL ANAEMIAAND THALASSAEMIAThe common and clinically important haemoglo-binopathies are due to production of abnormal ,Bchains (f chain abnormal haemoglobins) or inade-quate production of ,B chains (8 thalassaemia). Bothcx polypeptide chain abnormal haemoglobins and a.thalassaemia are relatively uncommon, the latterbeing considered briefly at the end of this section.Some polypeptide chain genes, eg, the y and pro-

bably the oa polypeptide chain genes of humanhaemoglobin, have duplicated, producing two lociresponsible for their polypeptide chain productionbut the father and mother still contribute an equalnumber of genes.

If a gene undergoes a mutation, that abnormalgene still carries the information to produce an endproduct almost identical to the original normal poly-peptide chain. However, at a single position, becauseof the mutation, a different aminoacid will be sub-stituted for the one that normally occurs at thatposition in the normal polypeptide chain. A severelymalfunctioning abnormal haemoglobin moleculemay result from the combination of haem with aglobin which possesses only this minute abnormality.

Other types of abnormal haemoglobins withaminoacid deletions or additions also exist. Again,abnormal polypeptide chains may be producedwhich contain conjoined parts of two different poly-peptide chains, eg, 8-f chains. All these variations ofabnormal haemoglobin are uncommon and onlythose abnormal haemoglobins (such as sickle-cellhaemoglobin) containing the single aminoacid sub-stitution need concern us.Commonly both genes for the f polypeptide chain

are normal and such a person is, at this gene locus, anormal homozygote. The normal gene may be called'A' (for adult haemoglobin). A normal person maybe represented by the figure

A A~which shows a section of the chromosomes carry

44

ing the structural genes responsible for ,B polypep-tide chain production. Gene

produces a normal fi polypeptide chain as is foundin normal adult haemoglobin. A person with twoA genes (genotype AA) will thus produce normaladult haemoglobin only.

Using such a diagrammatic approach a sickle-cell carrier and a patient with sickle-cell anaemiacould be illustrated as below:

Sickle-cell carrier Sickle-cell ancemia

Gene S produces the abnormal a polypeptide chaincharacteristic of sickle-cell haemoglobin (where theaminoacid valine has been substituted for glutamicacid in the sixth position of the f polypeptide chain).f thalassaemia may be illustrated in a similar way.

PThalossoemia minor 8Thalassaemia major(carrier state)

Genetic Counselling and Antenatal Diagnosis

Both sickle-cell anaemia and fi thalassaemia majorcan be avoided if carriers do not marry carriers.

SICKLE-CELL ANAEMIASickle-cell anaemia commonly results from the mat-ing of a sickle-cell carrier to a sickle-cell carrier(figure 1).

Sickle cell carrier

Reduction division

Random fertilization

ChildrenFig 1

R. G. Huntsman

If a sickle-cell trait carrier mates with a sickle-celltrait carrier on average one quarter of their childrenwill be normal, one half will be sickle-cell trait car-riers, and one quarter will have sickle-cell anaemia.With a carrier rate of 10 per cent (a reasonably

accurate figure for the negro population of GreatBritain), there is a one in a hundred chance of a car-rier marrying a carrier. It follows that there is a onein four hundred chance that a baby born to blackparents in the United Kingdom will have sickle-cellanaemia. These figures demonstrate that the virtuallysymptomless carrier state is common and thepotentially lethal disease state, sickle-cell anaemia, isby comparison very much rarer.

Sickle-cell carriers have red cells which containabout 25 per cent to 40 per cent of sickle-cellhaemoglobin and patients with sickle-cell anaemiahave red cells containing about 90 per cent of sickle-cell haemoglobin, the remaining 10 per cent beingmostly fetal haemoglobin. Tests which merelydetect sickle-cell haemoglobin, eg, the 'sickling' test,which uses intact red cells, and the widely usedsolubility tests, will give a positive result for both thecarrier and sickle-cell anaemia. Differentiationbetween these two conditions (which are clinically asdifferent as chalk and cheese) is best achieved in thelaboratory by electrophoresis, which separates nor-mal adult and sickle-cell haemoglobin by their differ-ent mobilities in an electric field. Ultimately afamily study may be invaluable to differentiate someof the more unusual haemoglobinopathies.Programmes designed to limit sickle-cell anaemia

by genetic counselling have been launched, especiallyamongst the black population of the United States.Their experience suggests that a hastily organizedprogramme may well be supported by inadequatediagnostic standards (Whitten, 1973). If such a pro-gramme is to be initiated in the United Kingdom theimpetus should come from the immigrant populationitself-a not unreasonable requirement consideringthe number of West Indian nurses in the NationalHealth Service. Such a programme would best beaimed at the level of the school leaver-old enough to

Father Mother

Haemoglobinopathies in pregnancy

understand the information given but withoutmarital attachments.

Screening of antenatal patients for 'sickling' (aterm best avoided as it obscures the fundamentaldifference between the carrier and the disease state)is liable to produce large numbers of sickle-cell car-riers in a condition too late to benefit immediately bygenetic counselling. If such a mother is demonstratedto be married to a sickle-cell carrier it is theoreticallypossible to offer her antenatal diagnosis and atherapeutic abortion if the fetus is found to havesickle-cell anaemia. At the present time, because ofthe small production of f polypeptide chains inearly pregnancy (nearly all the haemoglobin is fetalhaemoglobin), the techniques required for intra-uterine diagnosis are not refined enough to permitreliable clinical results before birth (Kan et al, 1972;Kazazian et al, 1972). However, neonatal diagnosisis possible using the cord blood samples. Such anearly diagnosis gives many advantages in arrangingmedical care for the baby even though, because ofthe high level of fetal haemoglobin present at birth,the symptoms of sickle-cell anaemia do not manifestthemselves in the first few months of life (Yawson etal, 1970).

P THALASSAEMIAfi thalassaemia is inherited in the same way as sickle-cell anaemia and if a fi thalassaemia minor (carrier)mates with a fi thalassaemia minor (carrier) onaverage one quarter of their children will be normal;one half will be carriers of a thalassaemia (8 thalas-

45

globins. Haemoglobin C is localized to West Africaand is also found in the New World Negro, many ofwhom originated from this area. The commonhaemoglobin D is called haemoglobin D Punjab, asthat area of the Indian continent is the main reser-voir. Finally, haemoglobin E occurs in a widespreadarea of the Far East, being found in the indigenouspopulation rather than in the newly arrived Chinese.It is thus apparent that some indication of theabnormal haemoglobin likely to be present in apatient will be obtained from a knowledge of theethnic origin, although such information is lessvaluable in areas of racial admixture such as Jamaica.Haemoblobins C, D and E all have aminoacid sub-stitutions in the fi polypeptide chain and thereforethe gene involved is the same as that in sickle-cellanaemia and fi thalassaemia, the a polypeptide chaingene. The carriers of haemoglobins C, D and E arequite symptomless and have normal haemoglobinlevels. The homozygote states, haemoglobin Cdisease, D disease and E disease are all chronichaemolytic anaemias of variable severity, usuallywith splenomegaly. Like any chronic haemolyticanaemia, eg, heriditary spherocytosis, the haemoglo-bin may fall as a result of marrow depression or anincreased rate of haemolysis, situations that may fol-low an infection. Again, the increased marrowactivity required to maintain a reasonable haemoglo-bin level demands extra folic acid and folic aciddeficiency may easily occur in pregnancy (figure 2).The inheritance would follow the pattern describedfor sickle-cell anaemia.

HaemoglobinC Hoemoglobin D Haemoglobin Ecarrier disease carrier disease carrier disease

Aig. 2

Fig. 2

saemia minor); and one quarter will die as childrenbecause they will have fi thalassaemia major.Adequate genetic counselling for this condition

must again depend upon accurate detection of car-riers. The problems involved in reliably detecting ,thalassaemia minor, especially in areas where irondeficiency is also endemic, are much greater than indetecting the sickle-cell carrier.

In-utero diagnosis of f thalassaemia major followedby therapeutic abortion is not yet a practical proce-dure (Nathan and Alter, 1975).

Haemoglobins C, D and E

There are three other common abnormal haemo-

Sickle-cell Haemoglobin C Disease

It is possible to have people carrying two abnormalbut different f polypeptide chain genes (doublyabnormal heterozygotes) and of the large number oftheoretical possibilities only two need concern ushere.

Sickle-cell haemoglobin C disease is the result ofinheriting one sickle-cell gene from one parent andone haemoglobin C gene from the other. Becausethere is no normal B polypeptide chain gene, thereare no normal P polypeptide chains produced andtherefore no normal adult haemoglobin (haemoglo-bin A). The genetic situation may be represented asfollows:

R. G. Huntsman

Sickle-cell haemoglobinC disease

This situation commonly comes about when a sickle-cell carrier mates with a haemoglobin C carrier, onein four children carrying both the sickle-cell and thehaemoglobin C gene (figure 3).

FatherSickle-cell and Chaemoglobin C arriers

Reduction division

Random fertilization

Children

the disease will usually behave in a relatively mildmanner, closer to that of the benign sickle-cell carrierthan to that of the severe sickle-cell anaemia (in thesickle-cell carrier, normal adult haemoglobin isalways the major part, which distinguishes this con-dition from sickle-cell B + thalassaemia where nor-mal adult haemoglobin is always the minor part).

Sickle-cell Haemoglobin

The main reservoir of sickle-cell haemoglobin is

Mother

Fig. 3

Sickle-cell ,8 Thalassaemia

The second doubly abnormal heterozygote whichwarrants special mention is sickle-cell fi thalas-saemia. Here one gene is the sickle cell f polypeptidechain gene and the other is a f thalassaemia gene.

Sickle-cell , Tholossoemia

L T4There are two types of f thalassaemia gene: the BO

type produces no f polypeptide chains and the B+type produces a few, although the normal productionrate has been considerably impaired. It thus followsthat in the sickle-cell 8 thalassaemia with the BO typeof thalassaemia gene there will be no normal fi poly-peptide chains produced, the BO thalassaemia genebeing totally inactive, and the patient will possessonly sickle-cell haemoglobin with a variable per-centage of fetal haemoglobin. Such a patient willbehave similarly to a case of sickle-cell anaemia. Thesickle-cell fi thalassaemia with the B+ type of thalas-saemia gene may produce enough fi polypeptidechains, the B+ thalassaemia gene having someactivity, to end with about 70 per cent sickle-cellhaemoglobin and 30 per cent of haemoglobin A.Such a patient will be protected by the relativelylarge amount of normal haemoglobin present and

central Africa (the carrier rate is commonly 20 percent) where it is limited to the north by the Saharadesert and Ethiopian highlands and to the south bythe rivers Zambesi in the east and Kunene in thewest. It is found to a much lesser extent in the MiddleEast, India and the Mediterranean (particularlyparts of Greece). In the New World, a sickle-cellhaemoglobin is found in the American and WestIndian Negro, who has a carrier rate of about 8 percent.

This widespread distribution of sickle-cell haemo-globin would make it obligatory to screen allpatients (even the native English) if no carriers are tobe missed. In clinical practice it is usual to concen-trate one's efforts upon the patient of Negro origin,as a screening programme involving all ethnic groupsis likely to exhaust the laboratory facilities.

Sickle-cell haemoglobin is the most important ofthe hundred or so abnormal haemoglobins identifiedbecause, when oxygen is removed from the red cell,sickle-cell haemoglobin crystallizes out of solutionand distorts the red cell into a sickle shape. When-ever this occurs, vessels may be blocked and the tis-sues fed by the vessels undergo infarction. Thisphenomenon of insolubility in the reduced form isnot possessed by the other abnormal haemoglobinsC, D and E.There are a number of genetically determined con-

ditions which have in common the presence withinthe red cell of a variable quantity of sickle-cellhaemoglobin (Hb S). These conditions vary in

46

Haemoglobinopathies in pregnancy

severity from, at one end of the clinical spectrum, thealmost completely benign sickle-cell carrier to-atthe other end-the patient with the potentiallylethal sickle-cell anaemia.The term 'sickle-cell disease' is confined to those

conditions where the presence of sickle-cell haemo-globin is commonly associated with symptoms, eg,sickle-cell anaemia, sickle-cell haemoglobin C diseaseand sickle-cell ,B thalassaemia. It is customary not toconsider the sickle-cell carrier as having sickle-celldisease, although even these fit carriers are liable onrare occasions to haematuria and, also, to infarctivecrises if oxygen tension is very greatly reduced.

Sickle-cell syndromes

Sickle-Cell Carrier Sickle-Cell Disease

I Sickle-cell anaemia2 Sickle-cell haemoglobin C disease3 Sickle-cell $ thalassaemia

In the United States literature 'sickle-cell disease' isoften synonymous with sickle-cell anaemia.

Sickle-cell Disease

CLINICAL COURSEA patient with sickle-cell disease usually maintains ahaematological and clinical condition which, for thatindividual, can be recognized as the 'steady state'. Itis important to collect the necessary data to establisha 'normal' haemoglobin level and other clinical para-meters for each patient. This can be best achieved byattendance at outpatient clinics, and specialized'sickle clinics' are being established which will pro-vide this information and at the same time offer conti-nuity of treatment. A deterioration (crisis) in this'steady state' may have an alarmingly sudden onsetand, on occasion, a fatal outcome.

INFARCTIVE CRISISThe commonest form of crisis in patients with sickle-cell disease is the infarctive crisis. This is caused bytangled sickled red cells obstructing blood vessels,which leads to tissue anoxia and ultimately to tissuedeath. Infarctive crises in bones, chest and abdomenare particularly common. Infarctions in the spleenare so common in sickle-cell anaemia that the spleenbecomes impalpable due to scarring (autosplenec-tomy): in contrast, a palpable spleen is common insickle-cell haemoglobin C disease and sickle-cell ,Bthalassaemia. Other sites for infarction are legion,and the patient may present with diagnoses asdivergent as rheumatism, meningitis and acuteappendicitis.

Infarctions of the bone marrow may result in sub-

47

sequent detachment of dead tissue into the circula-tion and the resulting pulmonary emboli may be thecause of sudden death (Shelly and Curtis, 1958).The pattern of infarction in pregnancy is much the

same as in the non-pregnant women except that theformer has an increased incidence of pelvic 'throm-boses' (presumably exacerbated or even caused byintravascular sickling) which may again cause pul-monary emboli (Adams et al, 1953).The increased incidence of eclampsia experienced

by pregnant women with sickle-cell disease mayagain be caused by thromboembolic phenomenatriggered off by intravascular sickling (Dale, 1949).

Patients who died of 'pseudo-toxaemia' (distin-guished, by a normal diastolic blood pressure, frompreeclampsia) were found to have marrow infarctionand pulmonary emboli (Fullerton et al, 1965;Hendrickse et al, 1972).

Infarctive crisis in the pregnant woman requiresparticularly careful evaluation, especially when pre-senting as abdominal pain. A too complacent label-ling of a patient as 'sickle crisis' may hide treatableobstetric hazards such as ectopic pregnancy orabruptio placentae (Pritchard et al, 1973).A number of factors capable of precipitating an

infarctive crisis are known and they are best avoided,if possible. They include infections (especially pul-monary infections) malaria, dehydration and vascu-lar stasis, acidosis, cold and anoxia.

Information on placental pathology is very limi-ted. Gross examination suggests normality(Hendrickse and Watson-Williams, 1966; Anderson,1971) but microscopy may demonstrate sickling inthe maternal sinuses (Anderson and Bushy, 1949;Adams et al, 1953; Song, 1971). The histologicaldemonstration of intravascular sickling does notnecessarily imply a physiological significance, as thechanges may occur after separation of the placenta.

APLASTIC CRISISThe aplastic crisis, caused by marrow depression, isassociated with infections, especially of viral type.Because of the short red cell life span even in the'steady state', a temporary depression of marrowactivity can, in sickle-cell anaemia, cause a catastro-phic fall in haemoglobin level and transfusion is thenneeded to maintain life. Marrow output failure mayalso result from a deficiency of folic acid, especiallyduring pregnancy. The very high maternal mortalityreported some years ago in Africa was greatlyreduced by folic acid supplements given during preg-nancy to patients with sickle-cell disease (Fullertonand Watson-Williams, 1962).

SEQUESTRATION CRISISThis crisis particularly, but by no means exclusively,

4. G. Huntsman

affects infants and young children. There is suddenmassive pooling of red cells, especially in the spleenand immediate transfusion is needed to maintainlife.

HAEMOLYTIC CRISISThe red cell life span, which is normal in the sickle-cell trait carrier, is shortened in all the varieties ofsickle-cell disease, being about 17 days in sickle-cellanaemia. Any given figure will vary from patient topatient, and in any particular patient the red cell lifespan may, perhaps as a result of infection, be sud-denly reduced (the haemolytic crisis) below the 'nor-mal' for that particular person.

Maternal Risk

All the above types of crisis can occur in both thepregnant and non-pregnant patient. The increasedmortality around the period of delivery suggests an

increased frequency and severity of crisis at that time.It has already been stated that folic acid therapy

will considerably reduce the maternal mortality. Irondeficiency is unusual in a chronic haemolyticanaemia, iron overload being a more usual problem.It must be remembered that on occasion irondeficiency can occur in patients with haemoglobino-pathies and that this complication may require cor-

rection (Anderson, 1972).Assuming that folic acid supplements are given, it

is difficult to be dogmatic about the maternal risk tobe expected. One of the major stumbling blocks toproviding information of value to the obstetrician isthe very variable severity of sickle-cell anaemia fromone patient to another. Indeed, any child who sur-vives until adolescence and, subsequently, becomespregnant may in any case be at the milder end of theclinical spectrum of this disease process (Apthorp etal, 1963). In some cases, attenuating factors such as

an unusually high level of fetal haemoglobin in thered cells (Charache and Conley, 1964) and the co-existence of cx thalassaemia, are known to lessen theseverity of sickle-cell anaemia (van Enk et al, 1972).In other cases the presence of another abnormalhaemoglobin, eg, haemoglobin Memphis, within thered cell reduces the severity of the sickling process

(Cooper et al, 1973). In many other cases where no

such factors are demonstrable and where environ-mental influences appear reasonably to be equal, it isinexplicable why some cases of sickle-cell anaemiashould run a severe course and others a mild.

Fort et al (1971) discuss this problem and point outthat overall maternal mortality figures would includegood-risk multiparous women with relatively benignsickle-cell anaemia having their fifth or sixth child.The inclusion of such cases would skew the results to

make them too optimistic for a girl presenting in herfirst or second pregnancy with sickle-cell anaemia ofaverage clinical severity. These authors suggest, afterexamining the records of 27 low-parity patients with57 pregnancies, that it would be reasonable to assumea maternal mortality for sickle-cell anaemia andsickle-cell haemoglobin C disease in the region of 10per cent. These figures may well be on the pessimisticside, and Pritchard et al (1973), for example, reportno maternal deaths in their series of 50 pregnanciesin 34 women with sickle-cell anaemia. They did,however, comment that maternal morbidity wasfrequent, at times intense and usually prolonged.Good obstetric management is likely to play a part

in reducing maternal mortality. Exhausting and diffi-cult labours are undesirable, but, as operative pro-cedures are not without risk, caesarian sectionsshould not be routinely undertaken (Morrison et al,1972). In considering transfusion it is important torealize that sickle-cell haemoglobin releases oxygenmore effectively than normal haemoglobin (Belling-ham and Huehns, 1968) and one should not be over-alarmed by low haemoglobin levels. Indeed, suddenovertransfusion may precipitate crisis by increasingblood viscosity. The level of haemoglobin at whichtransfusion is required is best judged by the clinicalcondition of the patient (Charache, 1974) and the'steady-state' haemoglobin level, if known. Theestablished infarctive crisis is difficult to treat(Huntsman, 1974), and, faced with a deterioratingclinical situation, a large-scale exchange transfusionmay have a place (Green et al, 1975). In a particularlytroublesome pregnancy partial exchange transfusionsmay have a prophylactic role (Morrison et al, 1972).

Relevant to obstetric management is the fact thatthe maternal mortality in other ethnic groups withsickle-cell anaemia is likely to be different from theNegro pattern. Saudi Arabians have an unusuallybenign form of this disease and not surprisingly nomaternal fatalities were reported from a seriesoriginating there where the usual clinical course ofsickle-cell anaemia is commonly alleviated by anunusually high level of fetal haemoglobin (Perrineand John, 1974).The preceding discussion has centred around

sickle-cell anaemia. Sickle-cell haemoglobin Cdisease has a somewhat different clinical course inthat the patients are often well and in many casesundiagnosed, their haemoglobin levels being some-times within normal limits. However, this diseaseprocess can produce the most violent, often unex-pected and sometimes fatal crisis which is prone to beespecially upsetting to the relatives, medical attend-ants and the coroner. In contrast, a typical patientwith sickle-cell anaemia tends to stumble from crisisto crisis and a fatal outcome lacks this unwelcome

48

Haemoglobinopathies in pregnancy

element of surprise. The obstetrician is ill advised toregard sickle-cell haemoglobin C disease as a 'mild'type of sickle-cell disease and in the series byPritchard et al (1973) of 78 pregnancies (43 women)two of the mothers with sickle-cell haemoglobin Cdisease died.The clinical course for sickle-cell f thalassaemia

depends on whether the : thalassaemia gene is of theBO or B+ type, ie, whether there is no normal adulthaemoglobin or whether there is about 30 per cent ofnormal adult haemoglobin. The former behaveclinically like sickle-cell anaemia and the latterusually behave clinically more like the sickle-celltrait, which is considered below.

Diggs (1973) has emphasized that well documentedstudies of maternal mortality, morbidity and neo-natal death are urgently needed to provide moremeaningful information than that at present avail-able to the obstetrician caring for a pregnantwoman with sickle-cell disease.

FETAL AND NEONATAL MORTALITY INMOTHERS WITH SICKLE-CELL DISEASEThe birth weight of babies of mothers with sickle-cellanaemia is below average (Anderson et al, 1960) andthe fetal wastage is high. The cause of neonatal deathappears to be somewhat obscure, the postmortemfindings being those of intrapartum anoxia (Ander-son, 1971). On occasion, maternal bone disease maylead to pelvic deformity and malpresentation(Akinla, 1973) and this complication could affect thedelivery ofmothers with sickle-cell disease (Hendrickseet al, 1972). Fort et al (1971) quote that, of 97pregnancies, there were 64 live births of which 50survived the neonatal period. Although these figuresare more pessimistic than others (Anderson, 1971;Pritchard et al, 1973), all workers in this fieldemphasize the high fetal and neonatal mortality. Itmust, in addition, be remembered that if married to asickle-cell carrier, half the children born will them-selves have sickle-cell anaemia, the mother passing asickle-cell gene to every offspring and the father toevery other. With a 10 per cent sickle-cell carrier rate,there is an overall 5 per cent chance of having a babywith sickle-cell anaemia. In advising a woman withsickle-cell disease on abortion and/or sterilization, itmust be remembered that a family may well throwadditional stress upon a woman who already carriesa heavy burden of disease. Contraceptive advice iscomplicated by possible adverse reactions to oralcontraception (Greenwald, 1970) but these risks areprobably smaller than the unwanted pregnancy(Charache, 1974).The fetal and neonatal mortality with mothers who

have sickle cell haemoglobin C disease appears to beeither roughly the same (Fort et al, 1971) or less

49

(Pritchard et al, 1973) than those expected frommothers with sickle-cell anaemia. One would envis-age that the fetal wastage resulting from pregnancyof mothers with sickle-cell f thalassaemia would bedependent upon the clinical severity of the mother'sdisease.

Sickle-cell Trait Carrier and Pregnancy

Low birth weights (Brown et al, 1972) and increasedperinatal mortality (Platt, 1971) have been reportedin the babies of sickle-cell carrier mothers. Themajority of opinion, however, considers that thesickle-cell trait carrier has no higher maternal riskof neonatal mortality than one would expect froma control group of women (Pearson and Vaughan,1969; De Lamerens et al, 1972; Pritchard et al,1973).However, as well as an increased liability to

haematuria, there also appears to be a higher inci-dence of bacteriuria in pregnancy and the sickle-celltrait mother could represent a high-risk group forurinary tract infection (Whalley et al, 1964). Certain-ly, pregnant women with sickle-cell anaemia havebeen found to have a predisposition to urinaryinfections in pregnancy (Beacham and Beacham,1951).On severe deoxygenation, the red cells of patients

with sickle-cell trait will eventually sickle and theoxygen tension at which this occurs can be easilyascertained in vitro. In vivo, sickling does not occur inareas where the arterial or venous p02 is easilymeasurable but it is more likely to take place in thebone marrow and splenic sinuses where vascular stasisis a normal feature of the circulation. This situationgreatly reduces the value of attempts to correlate thearterial or venous p02 measurements with infarctiverisk. However, even in the absence of scientific data,commonsense suggests that anaesthetic proceduresthat significantly reduce measurable p02 levels mustbe, to a greater or lesser extent, hazardous to thesickle-cell trait carrier.The percentage of sickle-cell haemoglobin in the

sickle-cell carrier varies from person to person andranges from about 20 per cent to 45 per cent. Itwould be expected that the red cells of those with thehigher percentage of sickle-cell haemoglobin willsickle at higher p02 levels and this can be demon-strated in vitro. It would be reasonable to assumethat such patients may be at especial risk during ananaesthetic accident (Howells et al, 1972). Unfor-tunately, data on the morbidity, if any, of the sickle-cell trait carrier are not readily available and the lackof animal models eliminates experimentation in vivo.It may be trite but it is also true to state that ananaesthetic that is inadequate for the sickle-cell trait

R. G. Huntsman

carrier is also inadequate for the middle-aged, some-what overweight male Caucasian!

Routine testing of pregnant women for sickle-cellhaemoglobin will produce a great majority of sickle-cell trait carriers and this information is currentlycarefully recorded and then ignored. In the future,some sickle-cell trait carriers may wish for geneticcounselling and, when practicable, those married tosickle-cell carriers may ask for antenatal diagnosis.Patients with sickle-cell anaemia are likely to bealready known and it would appear that the mainpurpose of antenatal testing for sickle-cell haemoglo-bin is to detect sickle-cell haemoglobin C disease: thepotentially unpleasant nature of this variety of sickle-cell disease has already been emphasized.

Beta Thalassaemia

Beta thalassaemia presents as a hypochromicanaemia, the red cells being pale because of theirlack of haemoglobin. In this case, the lack ofhaemoglobin is caused by the lack of globin (/3 poly-peptide chain production being impaired) and not alack of iron.

Beta thalassaemia is a relatively common disorder,being carried in racial groups spread across theMediterranean, Middle and Far East into China. Theoriginal name for / thalassaemia major, Mediter-ranean anaemia, because it was recognized by Cooleyin Italian immigrants to the United States, is clearlyfar too limiting and the obstetrician is just as likelyto meet this disorder in an Indian woman as in aCypriot. It is less usual but by no means rare to find/3 thalassaemia in a Negro, an ethnic group that isthe main reservoir of sickle-cell haemoglobin andhaemoglobin C.

BETA THALASSAEMIA MAJORBecause of the continuing production of fetalhaemoglobin during the first few months of life, thenewborn child with / thalassaemia major is at firstprotected from the severe anaemia resulting from thefailure of : polypeptide chain production. It is onlywhen the fetal haemoglobin production falls awayand adult haemoglobin fails to be produced, that thefull effects of this disease become clinically apparent.The severe anaemia that develops is associated withmassive hepato- and splenomegaly. The swelling ofthe marrow cavities results in some distortion of thenormal bone structure, the prominent zygomas, forexample, resulting in a characteristic 'mongoloid'facies. Beta thalassaemia major seldom presentsdiagnostic problems, because the parents of the childare in any case usually acquainted with the disease.A child with / thalassaemia major will be expected todie in childhood or adolescence and the presence of

this extremely unpleasant disease is incompatiblewith pregnancy.The obstetrician is, however, likely to be involved

in discussions concerning genetic counselling andantenatal diagnosis, which have already been con-sidered when the inheritance of / thalassaemia wasdiscussed.

BETA THALASSAEMIA MINOR ANDPREGNANCYThe normal haemoglobin in late pregnancy is hardenough to define and the 'normal' haemoglobin for apregnant woman with / thalassaemia minor isvirtually impossible to lay down. One has to remem-ber that these women even in the most unsophistica-ted conditions are able to reproduce effectively,otherwise this particular disorder would be too dis-advantageous to have increased to its present massiveproportions.

Because of the large-scale haematological screen-ing of antenatal patients, the obstetrician may wellbe the first medical attendant to be in a position todiagnose / thalassaemia minor. All too often, thepatient, because of a hypochromic anaemia, isassumed to be iron deficient and, when the responseto therapy is poor, the label is changed to some-thing such as 'iron-resistant anaemia'. The majordanger is that long-term iron medication may becontinued after delivery, because the patient may thenbe at risk of becoming iron overloaded.

It is, therefore, clearly important for the obstetri-cian to recognize the carrier of / thalassaemia andthen to prevent additional haematological stress byensuring folic acid supplements. Under these cir-cumstances one should hope to attain a haemoglobinwhich should be in the range of 10 g/dl (or above)and levels much below this would suggest additionalcomplications.

Beta thalassaemia minor can be suspected becausethe mean corpuscular haemoglobin (MCH) obtainedby an electronic cell counter is lower than that of ananaemic patient with a similar haemoglobin levelsuffering from iron deficiency. This is because thepatient with /3 thalassaemia minor has a greaternumber of red cells and the limited amount ofhaemoglobin available has to be shared out amongsta larger population. As a result, each red cell receivesless haemoglobin and this is manifested by anunusually low mean corpuscular haemoglobin.

Because, in /3 thalassaemia, only / polypeptidechain production is impaired, it would be reasonableto expect a normal or even increased amount of fetalhaemoglobin (0x2 y2) and haemoglobin A2 (0x2 82) tobe present, because these two haemoglobins containno /3 polypeptide chains. Nearly all cases of /3 thalas-saemia minor have a raised level of haemoglobin A2

so

Haemoglobinopathies in pregnancy

(recognized by electrophoresis or column chromato-graphy) and about half have a raised level of fetalhaemoglobin (recognized by an alkali denaturationtest or a 'Kleihauer' blood film stain, such as is usedto demonstrate transplacental haemorrhage).Although ,B thalassaemia minor is classically

associated with iron overload, it is becoming increas-ingly realized that women with this condition (evenin the absence of detectable haemorrhage) are by nomeans immune from iron-deficiency anaemia(Fleming and Lynch, 1969). It is, however, importantthat iron deficiency should be proven by a serum ironestimation before iron therapy is commenced. Incases of doubt, the marrow fragments can be stainedto give an estimate of the body iron stores.Problems arise when attempting to diagnose f

thalassaemia minor in the presence of iron deficiency.Not only is the reading of the electronic cell countercomplicated by a coexistent iron deficiency but alsothe haemoglobin A2 level may fall to normal in thepresence of this complication (Wasi et al, 1968). Inthese circumstances, it may be necessary to correctthe iron deficiency before recognizing the presence offi thalassaemia minor.

ALPHA THALASSAEMIAAlpha thalassaemia implies an impaired production(probably through deletion of structural genes) of apoylpeptide chains. The geographical distribution isnot clearly delineated but it may well be as wide-spread as is 8 thalassaemia. Because haemoglobinsA (a2 2), fetal haemoglobin (a2 y2) and haemoglobinA2 (U2 82) all contain a polypeptide chains, the pro-duction of all these three haemoglobins is impaired.As a result, and depending on the age of the patientand the severity of the disease, tetramers of y chains(Y4 or haemoglobin Barts) and f chains (P4 orhaemoglobin H) make their appearance.The inheritance of a thalassaemia is not clear

(Weatherall and Clegg, 1975) probably because the apolypeptide chain genes are duplicated giving a totalof four genes responsible for a polypeptide chainproduction.

Duplicatedacpolypeptide chain qenes

Whilst it may be oversimplified, it is useful to con-sider the clinical manifestations of a thalassaemia inthree categories of severity: (1) a thalassaemia major

51

(four a polypeptide chain genes deleted); (2) haemo-globin H disease (three cx polypeptide chain genesdeleted); and (3) a thalassaemia carrier states (one ortwo a polypeptide chain genes deleted).

ALPHA THALASSAEMIA MAJOR(HB BARTS HYDROPS SYNDROME)Alpha thalassaemia major has been described,especially amongst the Chinese, and is incompatiblewith delivery at term. In Malaysia, hydrops fetalis ismore often due to a thalassaemia than to maternal/fetal blood group incompatibility. Examinationof thehaemoglobin of the hydropic infant by electrophore-sis will demonstrate no haemoglobins containing apolypeptide chains, eg, no Hb A, a02 f2: Hb F, a2 y2:Hb A2, a2 82, the major haemoglobin being Y4 or HbBarts.

HAEMOGLOBIN H DISEASE AND PREGNANCYA less severe form of ax thalassaemia, compatiblewith pregnancy, is haemoglobin H disease. Patientswith this disease usually have a moderately severeanaemia, in the region of 8 to 10 g/dl, and somehepato and splenomegaly. Despite haematinics, thishaemoglobin level would tend to fall in pregnancy.The presence of haemoglobin H can be demonstratedby special staining of the red cells for inclusionscaused by the precipitation of the haemoglobin Hwithin the red cell (H body test) or alternatively byelectrophoresis.Such patients, who have a moderately severe

haemolytic process, benefit from permanent folicacid therapy which is obligatory in pregnancy. Thesituation as regards iron therapy is identical to thatdiscussed in P thalassaemia minor, iron deficiencyhaving to be proven before iron therapy is commen-ced.Drugs must be selected with care because of a pos-

sible adverse reaction to oxidant drugs such assulphonamides. These and other drugs, which canalso adversely affect patients who are glucose-6-phosphate dehydrogenase deficient, are best avoidedif alternatives are available. Transfusion may berequired to maintain a viable haemoglobin levelduring pregnancy.

CARRIERS OF ALPHA THALASSAEMIAThe carriers of a thalassaemia are difficult to detect.At birth they have a raised level of y4 (haemoglobinBarts) in their cord blood and later they may haveoccasional red blood cells which can be shown tocontain haemoglobin H inclusion bodies. It is alsopossible that the electronic red cell counter may offersome guidance in diagnosis (as in P thalassaemiaminor) and in cases of doubt the rate of a polypep-tide chain production may be measured using radio-

R. G. Huntsman

active isotopes. It is strange that using the criterion ofraised Hb Barts levels in the cord blood, a thalas-saemia minor would appear to be common inNegroes. Despite this apparently high carrier rate,haemoglobin H disease and cx thalassaemia major arevirtually unknown in this ethnic group.

Because the molecular lesion of ac thalassaemia isstill not clearly understood rational genetic counsel-ling would be difficult to carry out, even assumingthat carriers could be accurately identified.

Conclusion

The pathological processes to be expected in preg-nant patients with haemoglobinopathies mustdepend upon the establishment of an accuratediagnosis. Increasing emphasis is being laid upon theprevention of the possible complications, which havebeen outlined above, when the different disease pro-cesses are individually considered.

References

Adams, J. Q., Whitacre, F. E., and Diggs, L. W. (1953).Pregnancy and sickle cell disease. Obstet. and Gynec., 2,335-352.

Akinla, 0. (1973). Pregnancy and the skeletal complicationsof sickle cell disease. Postgrad. med. J., 49, 255-257.

Anderson, G. W., and Busby, T. (1949). Sickel cell anemiaand pregnancy. Amer. J. Obstet. Gynec., 58, 75-89.

Anderson, M. F. (1971). The foetal risks in sickle cell anae-mia. W. Indian med. J., 20, 288-295.

Anderson, M. F. (1972). The iron status of pregnant womenwith hemoglobinopathies. Amer. J. Obstet. Gynec., 113,895-900.

Anderson, M. F., Went, L, N., Maclver, J. E., and Dixon, H.G. (1960). Sickle-cell disease in pregnancy. Lancet, 2, 516-521.

Apthorp, G. H., Measday, B., and Lehmann, H. (1963).Pregnancy in sickle-cell anaemia. Lancet, 1, 1344-1346.

Beacham, W. D., and Beacham, D. W. (1951). Sickle celldisease and pregnancy: a review of the literature with aanalysis of the experience at the Charity Hospital, NewOrleans. Obstet. Gynec. Surv., 6, 455-483.

Bellingham, A. J., and Huehns, E. R. (1968). Compensationin haemolytic anaemias caused by abnormal haemoglobins.Nature (Lond.), 218, 924-926.

Brown, S., Merkow, A., Wiener, M., and Khajezadeh, J.(1972). Low birth weight in babies born to mothers withsickle cell trait. J. Amer. med. Ass., 221, 1404-1405.

Charache, S. (1974). The treatment of sickle cell anemia. Arch.intern. Med., 133, 698-705.

Charache, S., and Conley, C. L. (1964). Rate of sickling ofred cells during deoxygenation of blood from persons withvarious sickling disorders. Blood, 24, 25-48.

Cooper, M. R., Kraus, A. P., Felts, J. H., Ramseur, W. L.,Myers, R., and Kraus, L. M. (1973). A third case ofhemoglobin Memphis/sickle cell disease. Amer. J. Med.,55, 535-541.

Dale, M. (1949). Sickle-cell anemia complicated by preg-nancy. J. Mich., med. Soc., 48, 1484-1486 and 1530.

De Lamerens, S. A., Lopez-Duran, A., and Morrison, J. C.(1972). The offspring of patients with hemoglobin S. gene:preliminary report. Sth. med. J., 65, 537-539.

Diggs, L. W. (1973). Chapter 14, In Sickle Cell Disease:

Diagnosis, Management, Education, and Research, edited byH. Abramson, J. F. Bertles, and D. L. Wethers. Mosby,Saint Louis.

van Enk, A., Lang, A., White, J. M., and Lehmann, H.(1972). Benign obstetric history in women with sickle-cellanaemia associated with a-thalassaemia. Brit. med. J., 4,524-526

Fleming, A. F., and Lynch, W. (1969). Beta-thalassaemiaminor during pregnancy, with particular reference to ironstatus. J. Obstet. Gynaec. Brit. Cwlth, 76, 451-457.

Fort, A. T., and Morrison, J. C. (1972). Motherhood withsickle cell and sickle-C disease is not worth the risk. Sth.med. J., 65, 531-533.

Fort, A. T., Morrison, J. C., Berreras, L., Diggs, L. W, andFish, S. A. (1971). Counseling the patient with sickle celldisease about reproduction: pregnancy outcome does notjustify the maternal risk! Amer. J. Obstet. Gynec., 111, 324-327.

Fullerton, W. T., Hendrickse, J. P. De V., and Watson-Williams, E. J. (1965). Haemoglobin SC disease in preg-nancy. In Abnormal Haemoglobins in Africa, edited by J. H.P. Jonxis. Blackwell, Oxford.

Fullerton, W. T., and Watson-Williams, E. J. (1962).Haemoglobin SC disease and megaloblastic anaemia ofpregnancy. J. Obstet. Gynaec. Brit. Cwlth, 69, 729-735.

Green, M., Hall, R. J. C., Huntsman, R. G., Lawson, A.,Pearson, T. C., and Wheeler, P. C. G. (1975). Sickle cellcrisis treated by exchange transfusion. J. Amer. med. Ass.,231, 948-950.

Greenwald, J. G. (1970). Stroke, sickle cell trait, and oralcontraceptives. (Letter.). Ann. intern, Med., 72, 960.

Hendrickse, J. P. De V., Harrison, K. A., Watson-Williams,E. J., Luzzatto, L., and Ajabor, L. N. (1972). Pregnancy inhomozygous sickle-cell anaemia. J. Obstet. Gynaec. Brit.Cwlth., 79, 396-409.

Hendrickse, J. P. De V., and Watson-Williams, E. J. (1966).The influence of hemoglobinopathies on reproduction.Amer. J. Obstet. Gynec., 94, 739-748.

Howells, T. H., Huntsman, R. G., Boys, J. E., and Mahmood,A. (1972). Anaesthesia and Sickle-Cell Haemoglobin. Brit.J. Anaesth., 44,975-987.

Huntsman, R. G. (1974). Treatment of sickle-cell disease.Trans. roy. Soc. trop. Med. Hyg., 68, 80-84.

Kan, Y. W., Dozy, A. M., Alter, B. P., Frigoletto, F. D., andNathan, D. G. (1972). Detection of the sickle gene in thehuman fetus. New Engi. J. Med., 287, 1-5.

Kazazian, H. H., Jr., Kaback, M. M., Woodhead, A. P.,Leonard, C. O., and Nersesian, W. S. (1972). Furtherstudies on the antenatal detection of the sickle cell anemiaand other hemoglobinopathies. Advanc. exp. med. Biol.,28, 337-346.

Morrison, J. C., Fort, A. T., Wiser, W. L., and Fish, S. A.(1972) The modern management of pregnant sickle cellpatients: a preliminary report. Sth. med. J., 65, 533-536.

Nathan, D., and Alter, B. P. (1975). Antenatal diagnosis ofthe haemoglobinopathies. Brit. J. Haemat., 31, Suppl.,143-154.

Pearson, H. A., and Vaughan, E. 0. (1969). Lack of influenceof sickle cell trait on fertility and successful pregnancy.Amer. J. Obstet. Gynec., 105, 203-205.

Pembrey, M. E., and Weatherall, D. J. (1971). Maternalsynthesis of haemoglobin F in pregnancy. (Abstr.) Brit.J. Haemat., 21, 355.

Perrine, R. P., and John, P. (1974). Pregnancy in sickle-cellanemia in a caucasian group. Amer. J. Obstet. Gynec., 118,29-33.

Platt, H. S. (1971). Effect of maternal sickle-cell trait onperinatal mortality. Brit. med. J., 4, 334-336.

Pritchard, J. A., Scott, D. E., Whalley, P. J., Cunningham, F

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HaenzwglobinopathiesG., and Mason, R. H. (1973). The effects of maternalsickle-cell hemoglobinopathies and sickle-cell trait onreproductive performance. Amer. J. Obstet. Gynec., 117,662-670.

Shelley, W. M., and Curtis, E. M. (1958). Bone marrow andfat embolism in sickle cell anemia and sickle cell-hemoglo-bin C disease. Bull. Johns Hopk. Hosp., 103, 8-26.

Song, J. (1971). Pathology of Sickle Cell Disease, p. 149.Thomas, Springfield, Illinois.

Wasi, P., Disthasongchan, P., and Na-Nakorn, S. (1968). Theeffect of iron deficiency on the levels ofhemoglobins A2 andE. J. Lab. clin. Med., 71, 85-91.

Weatherall, D. J., and Clegg, J. B. (1975). Molecular basis ofthalassaemia. Brit. J. Haemat., 31, 133-141.

Whalley, P. J., Martin, F. G., and Pritchard, J. A. (1964).Sickle cell trait and urinary tract infection during preg-nancy. J. Amer. med. Ass., 189, 903-906.

Whitten, C. F. (1973). Sickle cell programming-an imperilled

promise. New Engl. J. Med., 288, 318-319.Yawson, G. I., Huntsman, R. G., and Metters, J. S. (1970).An assessment of techniques suitable for the diagnosis ofsickle-cell disease and haemoglobin C disease in cord bloodsamples. J. clin. Path., 23, 533-537.

General reading

Lehmann, H., and Huntsman, R. G. (1974). Man's Haemo-globins including the Haemoglobinopathies and theirLaboratory Investigation, 2nd ed. North-Holland, Amster-dam and Oxford.

Serjeant, G. R. (1974). The clinical features of sickle-celldisease North Holland Publishing Co Amsterdam, Oxford.

Song, J. (1971). Pathology of Sickle Cell Disease. Thomas,Springfield, Illinois.

Weatherall, D. J., and Clegg, J. B. (1972). The TholassaemiaSyndromes, 2nd ed. Blackwell, Oxford.

ain pregnancy 53