Parvovirus B19 and fetal/neonatal anaemia

Maternal infection with parvovirus B19 causes fetal anaemia which is severe enough to lead to intrauterine death in 9% of cases ( ; ; ). A diagnosis of fetal parvovirus B19 should be considered in every ‘unexplained’ case of fetal hydrops ( Table 30.5 ) since it has been estimated that parvovirus B19 is responsible for 15% of cases of non-immune hydrops ( ; ; ). In addition to anaemia, parvovirus infection causes marked reticulocytopenia (usually <10 × 10 ⁹ /l) and thrombocytopenia may also occur. The diagnosis of parvovirus B19 infection is primarily based on maternal serology together with the demonstration of B19 DNA in the fetus/neonate by dot blot hybridisation or polymerase chain reaction (PCR) ( ; ). Where results are negative on blood samples but clinical suspicion of parvovirus is high, PCR for B19 should also be carried out on bone marrow ( ). Management depends on the severity of the anaemia – severe cases diagnosed in utero may be treated by intrauterine transfusion; for those that survive, the majority have no long-term sequelae. However, a small number of neonates with chronic red cell aplasia, with or without evidence of persistent B19 DNA by PCR, have been reported, and for such cases intravenous immunoglobulin (IVIG) should be given to try and eradicate persistent viral infection ( ; ).

Diamond–Blackfan anaemia

The principal cause of congenital red cell aplasia is DBA ( ), which has an incidence of 5–7 cases per million live births. There is a clear family history in 20% of cases (both autosomal dominant and autosomal recessive inheritance are reported); the remaining 80% are sporadic. Affected children nearly always present in the first year of life; most diagnoses are made around 2–3 months of age, but 25% of cases present at birth and rare cases present as mid-trimester fetal anaemia and hydrops ( ; ). The usual presentation is with anaemia in an otherwise healthy baby; 40% of infants have associated congenital anomalies, particularly craniofacial dysmorphism, IUGR, neck anomalies (Klippel–Feil syndrome) and thumb malformations (e.g. triphalangeal or bifid thumbs) ( ; ) similar to those seen in Fanconi’s anaemia. The important laboratory features are normochromic anaemia (which may be macrocytic), reticulocytopenia and absent erythroid precursors on the bone marrow aspirate. It is important to exclude parvovirus infection by appropriate serology and dot blot testing, and Fanconi’s anaemia by diepoxybutane stress testing of peripheral blood lymphocytes ( ). If these tests are negative, the only other differential diagnosis of red cell aplasia with absent red cell precursors is transient erythroblastopenia of childhood, which, in contrast to DBA, resolves within a couple of months. Although bone marrow examination is required to diagnose DBA, other useful tests include red cell adenosine deaminase levels, which are elevated in most affected patients and sometimes in parents ( ) and genetic analysis for mutations in ribosomal protein genes, which are present in ~50% of families and can be investigated in specialised laboratories ( ). In the neonatal period, the treatment of DBA is red cell transfusion. Up to 75% of children with DBA respond to steroids and can often be weaned off transfusions, but this approach is not usually tried until after the first year of life ( ). DBA is a rather unpredictable disease: some cases resolve spontaneously; others wax and wane; but more than half of affected children have lifelong transfusion or steroid dependence and may be treated by bone marrow transplantation ( ; ).

Congenital dyserythropoietic anaemia

The CDAs are a rare group of disorders characterised by failure of red cell production due to ineffective erythropoiesis. Most cases are autosomal recessive and a history of parental consanguinity is not uncommon. In contrast to DBA, the bone marrow has vastly increased numbers of erythroid precursors but they are grossly abnormal and do not properly differentiate into mature RBCs. CDA usually presents during childhood. However, a number of neonates with CDA presenting at birth or during fetal life have been reported and in severe cases the presentation may be with hydrops fetalis ( ). Most affected babies are normally grown with no dysmorphic features, have a normocytic anaemia with normal white cells and platelets but a low reticulocyte count and transfusion-dependent anaemia. CDA type 1 is due to mutations in the codanin-1 gene ( ) and CDA type II, which is the most common type of CDA, has recently been shown to be due to mutations in the SEC23B gene ( ). The prognosis of CDA is extremely variable. For transfusion-independent children with CDA, lifespan is usually normal and quality of life is good. For transfusion-dependent children, the treatment options are:

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  splenectomy, which renders a small proportion of children transfusion-independent with a normal lifespan

  
  
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  bone marrow transplantation, the only curative treatment, but one which carries a 10% risk of mortality or graft rejection

  
  
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  lifelong red cell transfusion with iron chelation therapy, which carries a similar prognosis to children with β-thalassaemia major (i.e. median survival now >50 years with good treatment compliance).

Pearson syndrome

This rare disease is caused by mutations in mitochondrial DNA ( ). It often presents in neonates who are small-for-gestational-age and thrive poorly in the first few weeks of life ( ). The anaemia is normocytic and associated thrombocytopenia and neutropenia are common; abnormal leukocyte vacuolation may be seen in the peripheral blood and highly characteristic vacuolation of early erythoid cells on the marrow aspirate should prompt blood to be sent for mitochondrial DNA analysis to establish the diagnosis. The prognosis of Pearson syndrome is very poor: few children survive beyond the second year of life.

HDN due to ABO antibodies

ABO haemolytic disease occurs only in offspring of women of blood group O and is confined to the 1% of such women who have high-titre IgG antibodies. Haemolysis due to anti-A is more common (1 in 150 births) than anti-B. In contrast to anti-Rhesus antibodies, both anti-A and anti-B usually cause hyperbilirubinaemia without significant neonatal anaemia. This is mainly because there are relatively few group A or B antigen sites on neonatal red cells, allowing the antibody-coated cells to persist for longer in the circulation ( ). As a reflection of this, the blood film in ABO haemolytic disease characteristically shows very large numbers of spherocytes with little or no increase in nucleated red cells; this contrasts to rhesus HDN, where there are few spherocytes and vast numbers of circulating nucleated red cells. The DAT in ABO HDN may be negative. Management of ABO HDN usually just requires phototherapy; however, close monitoring is essential and exchange transfusion is occasionally required, particularly in cases of ABO HDN due to anti-B antibodies, which may cause severe anaemia as well as hyperbilirubinaemia ( ). Hydrops has occasionally been described.

Management of HDN

The antenatal diagnosis and management of pregnancies affected by red cell alloimmunisation require cooperation between obstetric, paediatric and haematology teams ( ). All neonates at risk should have cord blood taken for measurement of haemoglobin, bilirubin and a DAT and should remain in hospital until hyperbilirubinaemia and/or anaemia have been properly managed. Phototherapy should be given from birth to all rhesus-alloimmunised infants with haemolysis, as the bilirubin can rise steeply after birth and this expectant approach will prevent the need for exchange transfusion in some infants. In HDN due to anti-Kell, anaemia is usually more prominent than jaundice and minimal phototherapy may be necessary despite severe anaemia ( ). Systematic reviews have found that treatment of neonates with alloimmune haemolysis with IVIG does reduce the need for exchange transfusion ( ; ). Current National Institute for Health and Clinical Excellence guidance (neonatal jaundice) is to use IVIG when the serum bilirubin continues to rise at more than 8.5 µmol/l/h in spite of phototherapy, although further research is recommended.

Exchange transfusion in HDN is required for:

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  severe anaemia: haemoglobin <10 g/dl at birth (with the possible exception of anti-Kell, as mentioned above)

  
  
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  severe or rapidly increasing hyperbilirubinaemia

  
  
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  signs of bilirubin encephalopathy.

Details of the product to use for exchange transfusion are given on p. 782 and are summarised in the current .

‘Late’ anaemia presents at a few weeks of age in some babies with milder haemolytic disease who do not require exchange transfusion and in babies who have had earlier exchange transfusion. The blood film shows evidence of ongoing haemolysis and the anaemia is aggravated by the normal postnatal suppression of erythropoiesis. Such babies may require ‘top-up’ transfusion for symptomatic anaemia; conventional guidelines for neonatal transfusion can be followed (see Table 30.13 ) but irradiated blood must be used for infants previously receiving intrauterine transfusion, to prevent the risk of transfusion-associated graft-versus-host disease (TA-GVHD) ( ). Thus, all babies found to have a strongly positive DAT at birth and all treated by intrauterine transfusion must be followed up to monitor the rate of haemoglobin fall. It is important to note that administration of prophylactic antenatal anti-D to rhesus D-negative mothers quite commonly causes a weakly positive DAT in the baby at birth. Provided there is a clear history of antenatal prophylaxis and the Hb and the blood film are normal, it is not necessary to arrange further investigation and follow-up of such babies. It is worth noting that babies with ABO HDN rarely require ‘top-up’ transfusion unless severe anaemia in the first few days of life (Hb <10 g/dl) has been a feature. Where the haemoglobin is falling more rapidly than normal, particularly in babies with unconjugated hyperbilirubinaemia, monitoring must be continued until the jaundice resolves and the haemoglobin reaches a plateau. This may take 8 weeks and it may be helpful to ask the haematologist to review the blood films each time, to look for evidence of ongoing haemolysis. Folic acid (500 µg/kg/day) should be given to all babies with haemolytic anaemia until 3 months of age; folic acid is not necessary for babies with ABO HDN who are not anaemic. Erythropoietin has been used to prevent the need for ‘top-up’ transfusion for late anaemia; both failures and successes of this approach have been reported and erythropoietin is unlikely to prevent the need for transfusion where ongoing haemolysis is brisk ( ; ).

Hereditary spherocytosis

This is the commonest red cell membrane defect. It occurs in 1 in 5000 live births to parents of northern European extraction, but is less frequently seen in other ethnic groups ( ). It is autosomal dominant, but around 25% of cases are sporadic due to new mutations. Hereditary spherocytosis is genetically heterogeneous – mutations in spectrin, ankyrin, protein 4.1 and protein 3 have all been reported ( ). The usual presentation of hereditary spherocytosis in the neonate is with unconjugated hyperbilirubinaemia. Most affected neonates are not anaemic, but a small proportion have anaemia severe enough to require transfusion. The blood film in hereditary spherocytosis shows moderate numbers of spherocytes; the appearance is identical to that of ABO haemolytic disease, but the two disorders are distinguishable by the negative DAT in hereditary spherocytosis. While some babies will require one or two transfusions during the first 1–2 months of life, very few remain transfusion-dependent after this time and it is important to stop transfusions to evaluate the nadir haemoglobin reached. All children with hereditary spherocytosis should also receive folic acid supplementation (from 500 µg/kg/day in the first 6 months of life and a total daily dose of 2.5 mg from 6 months until 10 years of life, increasing to 5 mg daily thereafter). Splenectomy almost invariably induces complete remission of haemolytic anaemia (and therefore the need for folic acid prophylaxis) but is only indicated for more severely affected children and virtually always deferred until after the age of 6 years.

Hereditary elliptocytosis

This is a more complex disorder. It is caused by different mutations in the genes for spectrin, ankyrin or protein 4.1 ( ; ). In the common, autosomal dominant form of hereditary elliptocytosis, the heterozygotes have no clinical manifestations (i.e. no anaemia and no jaundice) apart from elliptocytes on the blood film. No treatment is required and folic acid prophylaxis is unnecessary, as folate deficiency is not a feature of this condition. Neonates who are homozygous or compound heterozygotes for hereditary elliptocytosis mutations have severe haemolytic anaemia; the most common form is HPP.

Hereditary pyropoikilocytosis

Neonates with HPP have more than one mutation in a red cell membrane protein (they may be homozygous or compound heterozygotes) ( ; ). HPP is uncommon but is important because it causes severe, transfusion-dependent haemolytic anaemia which does not improve with age. The diagnosis of HPP should easily be made by examining blood films from the baby (which shows lots of bizarre fragmented red cells and microspherocytes) and both parents (one or both often have red cell elliptocytosis); a useful diagnostic clue is the low MCV at birth (<60 fl). Red cell transfusion is usually necessary until the child is old enough to undergo splenectomy, to which there is an excellent response.

Glucose-6-phosphate dehydrogenase deficiency

G6PD deficiency is seen in all ethnic groups but has a high prevalence in individuals from central Africa (20%) and the Mediterranean (10%). The G6PD gene is on the X chromosome and therefore most affected neonates are boys, although female carriers may sometimes be identified as a result of neonatal jaundice screens. In neonatal G6PD deficiency, jaundice usually presents within the first few days of life and is often severe; anaemia is extremely rare and the blood film is completely normal, thus the diagnosis must be made by assaying G6PD on a peripheral blood sample ( ). It is not clear why some, but not all, G6PD-deficient neonates develop neonatal jaundice. In addition, the pathogenesis of the jaundice is also unclear, since most babies with G6PD deficiency have no evidence of haemolysis. The most important management issues in neonatal G6PD deficiency are close monitoring of the bilirubin, particularly where interactions with other risk factors for neonatal hyperbilirubinaemia are present, such as Gilbert syndrome or hereditary spherocytosis, since kernicterus has been reported in this setting ( ; ), and counselling parents of affected babies about which medicines, chemicals and foods may precipitate haemolysis ( Table 30.6 ). If exchange transfusion is required for severe hyperbilirubinaemia, conventional guidelines for exchange transfusion can be followed (see Chs29.2 , 44 ). Certain uncommon variants of G6PD deficiency are associated with chronic haemolysis, and for these children folic acid supplements should be given ( ). However, for the vast majority of patients there is no chronic haemolysis and no anaemia and therefore folic acid supplements are not indicated.

Pyruvate kinase deficiency

PK deficiency is the second most common red cell enzymopathy in neonates. It is autosomal recessive and clinically heterogeneous, varying from anaemia severe enough to cause hydrops fetalis to a mild unconjugated hyperbilirubinaemia ( ; ). In severe cases. the jaundice has a rapid onset within 24 hours of birth and exchange transfusion may be required ( ). The diagnosis is made by measuring pretransfusion red cell PK activity; in mild cases, the PK activity may be relatively modestly reduced, making the diagnosis difficult, and it is often useful to assay levels in the parents for confirmation. The blood film is sometimes distinctive but more often shows non-specific changes of non-spherocytic haemolysis and therefore it is good practice to assay PK in all babies with unexplained haemolysis after the common causes have been excluded. Management in the neonatal period depends on the severity of the jaundice and anaemia; some, but not all, children are transfusion-dependent and folic acid supplements should be given to prevent deficiency due to chronic haemolysis.

Other red cell enzymopathies presenting in neonates

The other red cell enzymopathies are rare. The most important to be aware of in the neonatal period is triosephosphate isomerase deficiency, which is autosomal recessive ( ). One-third of cases present with neonatal haemolytic anaemia and this may be the only presenting feature at this age; the devastating neurological features of this disorder only become apparent 6–12 months later ( ). Persistent haemolysis should therefore always be investigated.

Alpha-thalassaemia major

Alpha-thalassaemia major occurs when all four α-globin genes on chromosome 16 are deleted ( ). It predominantly affects families of south-east Asian origin and presents with mid-trimester fetal anaemia or hydrops fetalis which is fatal within hours of delivery (occasional babies have lived a few days). The only long-term survivors of α-thalassaemia major are those who received intrauterine transfusions ( ; ; ). In recent years there have been several reports of normal growth and development where intrauterine transfusion is commenced during the second trimester ( ; ); however, there is a high incidence of hypospadias in boys and other survivors have limb defects and/or severe neurological problems ( ; ). If intrauterine transfusions are delayed until the anaemia is severe, neonatal pulmonary hypoplasia is a cause of early mortality. The diagnosis of α-thalassaemia major should be suspected in any case of severe fetal anaemia presenting in the second trimester and any case of hydrops fetalis with severe anaemia in which the parents come from south-east Asia (it is also seen occasionally in families who originate from India, the Middle East or the Mediterranean). Checking the blood counts of the parents will immediately identify whether they are at risk of having a child with α-thalassaemia major – both parents will be carriers of a chromosome 16 in which both of the two α-globin genes are deleted and so they will have hypochromic, microcytic red cell indices (MCV usually <74 fl and MCH usually <24 pg). The diagnosis of α-thalassaemia major is confirmed by haemoglobin electrophoresis or HPLC (which shows only Hb Barts and Hb Portland; HbF and HbA are absent); the blood film shows hypochromic, microcytic red cells with vast numbers of circulating nucleated red cells. Neonatal management of α-thalassaemia major has no impact on survival unless the baby has received intrauterine transfusions; for these transfused neonates, management is the same as for β-thalassaemia, i.e. lifelong red cell transfusions or bone marrow transplantation after the age of 2 years ( ; ).

Alpha- and gamma-globin chain structural abnormalities

Most α- and γ-globin gene variants are clinically silent. Occasional α-globin gene variants may cause haemolytic anaemia in the newborn because when the abnormal α-globin associates with γ-globin the resultant haemoglobin is unstable whereas when the variant α-globin associates with β-globin the resultant haemoglobin is stable. An example of this is Hb Hasharon: α ^214Asp→His -γ ₂ is unstable; but as γ-globin chain production is physiologically switched off and β-globin chain production predominates, the α ^214Asp→His -β ₂ produced is stable and the haemolytic anaemia completely resolves ( ). A similar principle occurs in the γ-globin variant HbF-Poole, which causes neonatal haemolytic anaemia that resolves as the switch from γ- to β-globin occurs ( ). These variants can be identified by haemoglobin HPLC and are worth considering when commoner causes of haemolysis have been excluded.

Beta-thalassaemias and sickle-cell disease

Although these disorders are asymptomatic in neonates, if they are identified as a result of neonatal screening programmes, specialist advice should be sought as soon as possible. Babies with sickle-cell disease (homozygous sickle-cell disease, SC disease or S-β-thalassaemia) should be started on prophylactic penicillin V (62.5 mg twice daily) and folic acid (500 µg/kg/day) ( ). Babies with β-thalassaemia major usually start to require transfusion around the age of 6 months but benefit from folic acid supplementation until regular transfusions begin ( ).

Twin-to-twin transfusion

Twin-to-twin transfusion occurs in monochorionic twins with monochorial placentas ( Ch. 23 ) ( ). Bleeding may be acute, particularly during the second stage of labour, or chronic ( ). Chronic twin-to-twin transfusion can cause a marked difference in birthweight between twins, although recent studies show that the majority of twin pairs have a discordance in haemoglobin of <5 g/dl ( ). The diagnosis is now usually made in fetal life and antenatal treatment may be required ( Chs9 , 23 ). The donor twin is smaller and may be pale and lethargic or have overt cardiac failure; the recipient twin may be plethoric, with hyperviscosity and hyperbilirubinaemia and may rarely have a haemoglobin as high as 30 g/dl. Where the haemoglobin/haematocrit are very high, disseminated intravascular coagulation (DIC) can occur. Management of DIC is described on page 776 , and that of polycythaemia on page 767 .

Fetomaternal haemorrhage

This may occur spontaneously or secondary to trauma, such as road traffic accidents or falls. Most spontaneous fetomaternal bleeds occur in the third trimester or during labour. Fetomaternal bleeds may also be increased by invasive procedures such as fetal blood sampling and caesarean section. The degree of anaemia is variable and the clinical presentation depends on the amount and rate of blood loss. Most episodes involve very small quantities of blood (0.5 ml or less) but acute loss of >20% of the blood volume may cause intrauterine death, circulatory shock or hydrops ( ). Diagnostic clues are anaemia at birth in an otherwise well term baby with no or minimal jaundice. The most useful diagnostic tests are a DAT to exclude immune haemolysis, a reticulocyte count to exclude red cell aplasia, a Kleihauer test on maternal blood to quantify the number of HbF-containing fetal RBCs in the maternal circulation and a blood film ( ). Where the baby has bled acutely just prior to delivery, the blood film is normochromic/normocytic with large numbers of nucleated red cells. In this situation, the haemoglobin may be normal at delivery but fall rapidly as haemodilution occurs. Where there is chronic blood loss, the baby is often well but may present with cardiac failure; the blood film in this situation is hypochromic/microcytic, the nucleated red cells are less prominent and the Kleihauer result may be difficult to interpret. Another point of note is that, where there is ABO incompatibility between the mother and baby, the fetal cells may be rapidly destroyed within the maternal circulation – a high index of suspicion of fetomaternal haemorrhage as a cause of neonatal anaemia is needed because it is important to perform the Kleihauer test as soon as possible, to increase the chance of detection of fetal cells. In many cases, an acute fetomaternal bleed supervenes upon chronic fetomaternal blood loss. In this situation, severe anaemia (Hb <5 g/dl) has been shown to confer a poor prognosis, as most survivors have evidence of brain injury, although there are notable exceptions ( ).

The role of erythropoietin and haematinics

The severity of anaemia of prematurity and thereby the need for red cell transfusion can be reduced by a combination of the following approaches:

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  limiting iatrogenic blood loss by appropriate use of blood tests ( )

  
  
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  iron and folate supplementation for all preterm infants:

  
  
  
  
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    iron 3 mg/kg/day from 4–6 weeks of age (a pragmatic approach is to give 1 ml of sodium ironedetate (Sytron) once daily) or iron-fortified formula with 0.5–0.9 mg/dl iron ( ; ; )

    
    
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    folic acid 50 µg daily or 500 µg once weekly ( )

  
  
  
  
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  judicious use of erythropoietin ( ; ).

The many controlled trials of erythropoietin for prevention of neonatal anaemia have been extensively reviewed ( ), including two meta-analyses ( ; ), and are only briefly summarised here. Recombinant erythropoietin is biologically effective in that it stimulates erythropoiesis in all preterm infants and there is no evidence of erythropoietin insensitivity. Erythropoietin is also able to reduce red cell transfusion requirements in preterm infants ( ; ; ; ; ). However, in most studies there is no evidence to support the clinical effectiveness of erythropoietin, i.e. that it reduces the number of transfusions to an extent which demonstrably reduces the hazards of transfusion. At best, the studies show that erythropoietin reduces the number of transfusions in relatively well infants with low transfusion requirements ( ; ; ; ). One study has shown that the use of erythropoietin together with careful nutritional supplementaion and judicious use of laboratory tests to reduce iatrogenic blood loss can halve the transfusion requirements in a cohort of sick extremely-low-birthweight neonates ( ). However, most studies have shown that, even in high doses, the erythropoietin-mediated increase in red cell production is unable to increase sufficiently to cope with the need for frequent phlebotomy and multiple transfusions in sick preterm infants ( ; ). Despite its marginal role in reducing transfusion requirements, erythropoietin may become more important again if worries over the safety of blood transfusion lead to reduced availability and parental acceptance of red cell transfusion. At present, the main therapeutic roles for erythropoietin in neonates are:

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  in preventing anaemia in infants who have received intrauterine transfusions for alloantibody-mediated anaemia ( )

  
  
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  in a non-emergency situation where red cell transfusions are against the parents’ wishes and are not felt to be absolutely essential to save the life of the baby (e.g. preterm babies of Jehovah’s witnesses) ( ).

An effective dose of recombinant erythropoietin in this setting is 300 µg/kg as a single subcutaneous injection three times per week starting in the first week of life. Epoetin-β should be used in view of the potential risk of red cell aplasia described (in adults) with epoetin-α, the alternative form of recombinant erythropoietin ( ). This is because the haemoglobin does not start to rise until about 10–14 days after erythropoietin has been commenced. In addition, iron supplements (Sytron, as above) should be started as soon as possible, to prevent the rapid development of iron deficiency in erythropoietin-treated infants (the dose may need to be increased up to a maximum of 9 mg/kg if iron deficiency develops on the standard dose of Sytron) ( ).