Antenatal management of severe feto-maternal alloimmune thrombocytopenia: HLA incompatibility may affect responses to fetal platelet transfusions

In feto-maternal alloimmune thrombocytopenia (FMAIT), severe hemorrhage, particularly intracranial haemorrhage (ICH), may occur before delivery. Management strategies to prevent ICH in high-risk pregnancies include maternal administration of intravenous Ig with or without steroids and fetal platelet transfusions. This report describes a patient who lost three fetuses with ICH because of FMAIT due to anti- HPA-1a. ICH occurred earlier in successive pregnancies (at 28, 19, and 16 weeks of gestation) despite maternal treatment with intravenous Ig and steroids from 14 weeks of gestation in the third pregnancy. The fourth pregnancy was managed by administering weekly intraperitoneal injections of Ig to the fetus from 12 to 18 weeks of gestation. At 18 weeks, there was no evidence of ICH, but the fetal platelet count was only 12 x 10(9)/L. Serial fetal platelet transfusions were started, but there were poor responses because of immune destruction of the transfused platelets by maternal HLA antibodies. There were improved responses to transfusions prepared from the mother and from HLA- compatible HPA-1a-negative donors. At 35 weeks of gestation, a normal infant was delivered by Caesarean section after 20 platelet transfusions. There was prolonged thrombocytopenia in the baby for 15 weeks after birth, probably due to transfer of HPA-1a antibodies in the transfusions of unwashed maternal platelets. The optimal management of pregnancies likely to be severely affected by FMAIT is still evolving. Intensive management was successful in this case, but a successful outcome cannot be guaranteed in severely affected cases. This is the first time that HLA incompatibility has been found to complicate fetal transfusion therapy.     

European collaborative study of the antenatal management of feto-maternal alloimmune thrombocytopenia

The aims of this study were to determine whether the severity of fetomaternal alloimmune thrombocytopenia (FMAIT) in the current pregnancy could be predicted from the history of FMAIT in previous pregnancies, and to assess the effects of different types of antenatal intervention. Fifty-six fetuses were studied that all had a sibling affected by FMAIT due to human platelet antigen 1a (HPA-1a) alloimmunization. Cases with a sibling history of antenatal intracranial haemorrhage (ICH) or severe thrombocytopenia (platelet counts of < 20 x 109/l) had significantly lower pretreatment platelet counts than cases whose siblings had less severe thrombocytopenia or postnatal ICH. Maternal therapy resulted in a platelet count exceeding 50 x 109/l in 67% of cases. None of the fetuses managed by serial platelet intrauterine transfusions (IUT) suffered ICH following treatment. However, several serious complications arose with fetal blood sampling (FBS). Overall, intervention improved outcome, as three study cases suffered from antenatal ICH and three others died whereas 15 study cases had a sibling with an ICH, eight of whom died. The results of this study suggest that the start of therapy can be stratified on the basis of the sibling history of FMAIT, and support the use of maternal therapy as first-line treatment.     

Fetal and neonatal alloimmune thrombocytopenia: recommendations for evidence-based practice,an international approach

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) may result in severe bleeding, particularly fetal and neonatal intracranial haemorrhage (ICH). As a result, FNAIT requires prompt identification and treatment; subsequent pregnancies need close surveillance and management. An international panel convened to develop evidence-based recommendations for diagnosis and management of FNAIT. A rigorous approach was used to search, review and develop recommendations from published data for: antenatal management, postnatal management, diagnostic testing and universal screening. To confirm FNAIT, fetal human platelet antigen (HPA) typing, using non-invasive methods if quality-assured, should be performed during pregnancy when the father is unknown, unavailable for testing or heterozygous for the implicated antigen. Women with a previous child with an ICH related to FNAIT should be offered intravenous immunoglobulin (IVIG) infusions during subsequent affected pregnancies as early as 12 weeks gestation. Ideally, HPA-selected platelets should be available at delivery for potentially affected infants and used to increase the neonatal platelet count as needed. If HPA-selected platelets are not immediately available, unselected platelets should be transfused. FNAIT studies that optimize antenatal and postnatal management, develop risk stratification algorithms to guide management and standardize laboratory testing to identify high risk pregnancies are needed.     

Monitoring Anti-HPA-1a Platelet Antibody Levels during Pregnancy Using the MAIPA Test

Anti-HPA-1a platelet antibody levels in pregnant women with a history of fetomaternal alloimmune thrombocytopenia (FMAIT) were monitored longitudinally using the monoclonal antibody immobilisation of platelet antigens (MAIPA) assay, in order to examine any variation in optical density (OD) readings obtained over the course of pregnancy and after delivery. Seven women were selected; 4 were studied retrospectively and 3 prospectively (the latter being treated with intravenous gammaglobulin; IVGG). Levels of anti-HPA-1a were measured at various intervals after delivery of the first affected infant, to post delivery of the following affected infant. A decrease in MAIPA OD was demonstrated in all patients during the course of these pregnancies. This assay is a useful tool for monitoring anti-HPA-1a in women with a history of infants affected with FMAIT. A maternal antibody 'resting' level prior to, or early in the first trimester, must be established for comparison.     

Alloimmune thrombocytopenia of the fetus and the newborn

Fetal/neonatal alloimmune thrombocytopenia results from a maternal alloimmunization against fetal platelet antigens. Care must be taken in making a correct diagnosis that eliminates other causes of thrombocytopenia that may occur during pregnancy. Biological diagnosis is normally made by platelet genotyping and search for the maternal alloantibody using monoclonal antibodies in an antigen capture assay. Fetal alloimmune thrombocytopenia, when severe, may result in intracerebral hemorrhage leading to hydrocephalus and death of the fetus. Neonatal alloimmune thrombocytopenia may be present in an otherwise healthy infant. While screening procedures are not in place to detect fetal/neonatal alloimmune thrombocytopenia, it is true that fetal hydrocephalus, unexplained fetal thrombocytopenia with or without anemia, or recurrent miscarriages should be adequate indicators for suspecting fetomaternal alloimmune thrombocytopenia. Multiparous women with a history of giving birth to at least one alloimmune thrombocytopenic infant should be carefully monitored in subsequent pregnancies. Postnatal management of neonatal alloimmune thrombocytopenia involves compatible platelet transfusion in the neonate. Antenatal management of fetal alloimmune thrombocytopenia is controversial and includes a combination of maternal intravenous gamma globulin (i.v.IgG) administration, intrauterine platelet transfusions, and corticosteroid therapy, while monitoring fetal platelet counts closely throughout the course of pregnancy. Screening of pregnant women may become a public health issue only after antenatal therapy is more standardized.     

A new efficient tool for non-invasive diagnosis of fetomaternal platelet antigen incompatibility

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is the consequence of platelet destruction by maternal alloantibodies against fetal human platelet antigens (HPA). This may result in intracranial haemorrhages (ICH) or even fetal death. Currently, fetal HPA genotyping is performed using invasive procedures. Here, we carried out a proof-of-concept study for non-invasive prenatal diagnosis of fetal platelet genotyping in four HPA systems (HPA-1, -3, -5 and-15) by droplet digital polymerase chain reaction (ddPCR) using cell-free DNA extracts from the plasma of 47 pregnant women with suspected, or history of, FNAIT. Results showed that 74% (35/47) of pregnant women presented incompatibility in at least one HPA system, and 38% (18/47) of cases presented HPA-1 incompatibility, including nine women with multiple incompatibilities. ICH occurred in one case of profound fetal thrombocytopenia with HPA-15 incompatibility, confirming the need for non-invasive prenatal genotyping in systems other than HPA-1. Fetal HPA genotypes predicted by ddPCR were confirmed in all FNAIT cases after amniocentesis or delivery. Fetal HPA genotyping on maternal plasma based on ddPCR is a fast, safe and reliable non-invasive method. This technique will be useful for the early identification of pregnancies at high risk of FNAIT requiring antenatal management to minimize the risk of fetal/neonatal haemorrhage.     

The management of alloimmune neonatal thrombocytopenia.

Neonatal alloimmune thrombocytopenia (NAITP), defined as thrombocytopenia (platelet count < 150 x 10(9)/l) due to transplacentally acquired maternal platelet alloantibodies, occurs in approximately 1 per 1200 live births in a Caucasian population. In such a population, the majority (> 75 percent) of cases are due to fetomaternal incompatibility for the platelet specific alloantigen, HPA-1a (P1A1, Zwa). Incompatibility for the HPA-5b (Bra) alloantigen is the next most frequent cause of NAITP in Caucasians; much less common is NAITP due to incompatibility for HLA, blood group ABO or other platelet-specific antigens. In non-Caucasian populations (e.g. Orientals) HPA-1a incompatibility is a rare cause of NAITP and other alloantigens e.g. HPA-4b (Penb, Yuka) are implicated. The greatest clinical challenge relates to the antenatal management of pregnant women alloimmunized to the HPA-1a (P1A1, Zwa) antigen, and particularly the subset of such women who have a history of a previously affected infant with severe thrombocytopenia and/or intracranial hemorrhage (ICH). The risk of antenatal ICH in the fetus of such women is high enough to merit intervention, either weekly infusion of high-dose intravenous immunoglobulin G (IVIG) with or without corticosteroids given to the mother (the preferred approach in North American centres), or repeated in-utero fetal platelet transfusions (the preferred treatment approach in some European centres). Post-natal management of severely affected infants centres on the rapid provision of compatible antigen-negative platelets harvested from the mother or a phenotyped donor. The value of antenatal screening programs to detect 'at risk' alloimmunized women during pregnancy continues to be debated.     

The prenatal identification of fetal compatibility in neonatal alloimmune thrombocytopenia using amniotic fluid and variable number of tandem repeat (VNTR) analysis

Summary. Most severe episodes of neonatal alloimmune thrombocytopenic purpura (NATP) are caused by antiplatelet alloantibodies against the HPA-la (Pl^A1) antigen. However, half of subsequent fetuses produced from a HPA-la/b father (genotypic frequency 28%) will result in a child who is not affected. Some investigators manage NATP by confirming the fetal platelet phenotype using percutaneous umbilical cord sampling, a procedure that carries a low but real risk of fetal morbidity and mortality. More recently, physicians determine the fetal platelet antigen genotype using DNA derived from amniotic fluid or chorionic villus samples. All therapy is withdrawn for a fetus who genotypes as HPA-lb/b. However, since the fetus is the same genotype as the mother, there can be uncertainty about the origin of the genetic material and thus the validity of the fetal genotype. The inappropriate withdrawal of therapy for a erroneously genotyped fetus could be fatal, and consequently many physicians advocate fetal HPA-1 phenotyping with confirmation using percutaneous umbilical blood sampling. In this report we describe the management of two pregnancies with previously affected infants due to anti-HP A-la alloantibodies. Both husbands were HPA-la/b. For the current pregnancies, amniotic fluid was collected at 20 or 29 weeks of gestation, and the platelet genotype indicated that the fetuses were HPA-lb/b. The fetal origin of the amniotic fluid derived DNA was confirmed by the forensic technique of DNA profiling using variable number of tandem repeat (VNTR) analysis. All therapy was withdrawn, percutaneous umbilical blood sampling was not performed, and both women vaginally delivered healthy non-thrombocytopenic infants. The application of platelet alloantigen genotyping using DNA from amniotic fluid cells identified the HPA-lb/b fetus, and VNTR analysis confirmed that the tissue was fetal derived, thus avoiding the necessity for percutaneous umbilical blood sampling. The use of this approach in patients at risk will avoid additional investigation and treatment in approximately one-seventh of all NATP pregnancies involving the HPA-la antigen.     

Thrombocytopenia and disorders of platelet function in pregnancy

Pregnancy is associated with physiological and pathological changes in platelet numbers and function, which can be of clinical concern because of risks for maternal and fetal or neonatal bleeding. Thrombocytopenia in pregnancy is frequently encountered and may be due to increased platelet turnover and plasma dilution, immune-mediated mechanisms, or a complication of a more severe underlying pregnancy-related disorder such as preeclampsia. Inherited defects in platelet function and number may also manifest during pregnancy with the risk of bleeding dependent on the underlying problem. In some women, the diagnosis of thrombocytopenia will precede pregnancy but in others, the problem is first identified when routine pregnancy blood tests are performed. An accurate diagnosis and risk assessment in the antenatal period are essential for developing specific plans for any antenatal interventions and for management of delivery and the postpartum periods, and the neonate. Management of pregnant women with platelet disorders requires a multidisciplinary approach and close collaboration between the obstetric and hematology teams.     

In vitro culture of colony forming unit-megakaryocyte (CFU-MK) in fetal alloimmune thrombocytopenia

Summary . Perinatal alloimmune thrombocytopenia (PAITP) causes intracranial haemorrhage in the fetus and neonate. However, the severity of the thromobocytopenia correlates poorly with maternal anti-platelet antibody titres. To test the hypothesis that reduced platelet production contributes to fetal thrombocytopenia in PAITP, maternal sera from three HPA-la-negative mothers whose pregnancies were complicated by anti-HPA-la (two severe cases, one mild case) were added to colony forming unit-megakaryocyte (CFU-MK) cultures from HPA-la positive and negative individuals. Sera from the two severely affected pregnancies containing anti-HPA-la caused 66–100% inhibition of HPA-la-positive fetal and neonatal CFU-MK, whereas CFU-MK from two HPA-la-negative mothers were not inhibited by the anti-HPA-la-containing sera. Maternal serum from the case of mild PAITP caused only mild inhibition of HPA-la-positive cord and adult CFU-MK and did not inhibit HPA-la-positive fetal CFU-MK. Taken together, these findings suggest that reduced megakaryocyte production contributes to fetal thrombocytopenia due to maternal anti-HPA-la antibodies and also that the degree of CFU-MK inhibition correlates with severity of fetal thrombocytopenia.     

Screening Programmes for Foetomaternal Alloimmune Thrombocytopenia

Screening to detect pregnancies at risk of severe thrombocytopenia due to Foetomaternal alloimmunisation to Human Platelet Alloantigens (FAIT) is not yet a standard of care. Screening may be performed antenatally with the possibility of early intervention/therapy. Post natal measurement of cord platelet count may not always prevent fetal damage but may detect severe thrombocytopenia from other causes. Assessment of FAIT screening against World Health Organisation standards for screening programmes helps define areas where knowledge is still lacking and where research effort should be directed. Limitations to screening have been lack of reliable assays for typing and antibody detection, a limited understanding of the relationship between the presence of alloantibodies and clinical disease, inability to predict non-invasively which cases will have a severe outcome, and controversy as to which antenatal therapy is optimal for cases at high risk of a poor outcome.     

Feto-maternal alloimmune thrombocytopenia: antenatal therapy with IvIgG and steroids — more questions than answers

The optimal antenatal therapy for fetal thrombocytopenia has not been determined. We analysed 37 cases managed by maternal therapy and observed a successful outcome of maternal treatment in 26% of IvIgG cases and in 10% of steroid-treated cases. The significance of a plateau of the fetal platelet counts during pregnancy, 41% of IvIgG cases and 20% of cases treated with steroids, is uncertain. It may indicate a stabilization of thrombocytopenia, hence a beneficial effect of therapy, or the natural course of the platelet count in a low-risk pregnancy. Overall outcome was unpredictable, but amongst the therapy failures there were proportionally more severely affected siblings. Further multicentre studies are necessary to establish the optimal antenatal management of high-risk pregnancies.     

Fetal alloimmune thrombocytopenia and maternal intravenous immunoglobulin infusion

Background

Different therapeutic approaches have been used in fetal-neonatal alloimmune thrombocytopenia, but many centers administer immunoglobulin G infusions to the pregnant woman. We studied the effect of maternal antenatal immunoglobulin infusions on fetal platelet counts in pregnancies with fetal alloimmune thrombocytopenia.

Design and Methods

We retrospectively analyzed the clinical courses of fetuses with fetal alloimmune thrombocytopenia whose mothers were treated with immunoglobulin G infusions in a single center between 1999 and 2005. In a center-specific protocol, weekly maternal immunoglobulin G infusions were given to 25 pregnant women with previously affected neonates and four women with strong platelet antibodies, but no previous history of fetal alloimmune thrombocytopenia; before each infusion diagnostic fetal blood sampling was performed to determine fetal platelet counts and immunoglobulin G levels.

Results

There were 30 fetuses with fetal alloimmune thrombocytopenia, confirmed by initial fetal blood sampling showing fetal platelet counts between 4×10⁹/L and 130×10⁹/L and antibody-coated fetal platelets using a glycoprotein specific assay. Despite weekly antenatal maternal immunoglobulin G infusions fetal platelet counts did not change significantly. Maternal and fetal immunoglobulin G levels, measured before every infusion, increased significantly with the number of maternal immunoglobulin G infusions.

Conclusions

In this group of fetuses with fetal alloimmune thrombocytopenia no consistent increase of fetal platelets was achieved as a result of regular maternal immunoglobulin G infusions.     

Changes in antithrombin activity and platelet counts in the late stage of twin and triplet pregnancies

It is possible that women with triplet pregnancies are more likely to exhibit pregnancy-induced antithrombin deficiency, gestational thrombocytopenia, and perinatal elevation in serum aspartate aminotransferase (AST) than women with twin pregnancies. We retrospectively reviewed changes in antithrombin activity, platelet count, and blood chemistry in 23 twin and seven triplet pregnancies in which the mothers received antenatal care and gave birth in our hospital during 1999 and 2001. Both antithrombin activity and platelet counts gradually decreased until delivery, then promptly increased after delivery in both twin and triplet pregnancies. A significantly larger number of women developed gestational thrombocytopenia of < 100 x 10 (9)/L (43% [three of seven] versus 4.3% [one of 23]; p < 0.01) and pregnancy-induced antithrombin deficiency of < 60% of normal activity (57% [four of seven] versus 17% [four of 23]; p < 0.05) in triplet than in twin pregnancies. Eight women with pregnancy-induced antithrombin deficiency, including three women with gestational thrombocytopenia, were significantly more likely to develop perinatal elevations of AST, lactate dehydrogenase, serum creatinine, fibrin/fibrinogen degradation products, and D-dimer than were those without pregnancy-induced antithrombin deficiency. These findings suggest that women with triplet pregnancies are at an increased risk of the HELLP syndrome and acute fatty liver of pregnancy compared with women with twin pregnancies.     

A retrospective 11-year analysis of obstetric patients with idiopathic thrombocytopenic purpura

Numerous studies have examined the outcomes of infants born to mothers with idiopathic thrombocytopenic purpura (ITP). Fewer studies have discussed the morbidity of obstetric patients with ITP. We describe a retrospective study of 92 women with ITP during 119 pregnancies over an 11-year period. Most women had thrombocytopenia during pregnancy. At delivery, women in 98 pregnancies (89%) had platelet counts lower than 150 x 109/L; most had mild to moderate thrombocytopenia. For many, the pregnancy was uneventful; however, women had moderate to severe bleeding in 25 pregnancies (21.5%). Women in 37 pregnancies (31.1%) required treatment to increase platelet counts. During delivery, 44 women (37.3%) received epidural analgesia without complications, with most having a platelet count between 50 and 149 x 109/L. Most deliveries (82.4%) were vaginal. Bleeding was uncommon at delivery. Infant platelet counts at birth ranged from 12 to 436 x 109/L; 25.2% of infants had platelet counts lower than 150 x 109/L, and 9% had platelet counts lower than 50 x 109/L. Eighteen infants (14.6%) required treatment for hemostatic impairment. Two fetal deaths occurred. One was caused by hemorrhage. ITP in pregnancy carries a low risk, but mothers and infants may require therapy to raise their platelet counts.     

Alloimmunization to the PIA1 platelet antigen: results of a prospective study

The natural history of alloimmunization to the PlA1 platelet antigen is uncertain. We followed 50 PlA1-negative pregnant women during pregnancy and for 6 months post-partum in order to determine this natural history. The cohort of PlA1-negative women was obtained by PlA1 typing 5000 women. Three PlA1-negative women formed anti-PlA1 antibodies during this prospective study, two in pregnancy and one in the immediate post-partum period. All three PlA1 antibody producers were HLA-DR3 positive, a histocompatibility phenotype that is strongly associated with alloimmunization to the PlA1 antigen. One of the three infants delivered to these mothers was thrombocytopenic (platelet count 9 x 10(9)/l). The remaining two infants had normal platelet counts at birth (160 and 174 x 10(9)/l). The HLA-A1, -B8, -DR3 and -DRw52 phenotype frequencies in the group of PlA1-negative women who did not form PlA1 antibodies (n = 47) was similar to that found in their husbands, and that expected in a normal Caucasian population. From our data we estimate that alloimmunization to the PlA1 antigen occurs in approximately one out of every 1000 pregnancies in a Caucasian population. It is important to recognize that not all pregnancies in which a mother has formed PlA1 alloantibodies will result in the delivery of a thrombocytopenic infant. These findings are relevant to programs designed to either prevent alloimmunization to the PlA1 antigen (through passive administration of anti-PlA1 immunoglobulin to at-risk PlA1-negative mothers), or to identify women at risk of delivery of thrombocytopenic infants (by antenatal screening to detect women alloimmunized to the PlA1 antigen).     

Severe Neonatal Alloimmune Thrombocytopenia due to Anti-HPA-3a

Background and Objectives: Neonatal alloimmune thrombocytopenia is usually attributable to HPA-la antibodies. We report a case of parental platelet antigen incompatibility associated with a severe neonatal thrombocytopenia secondary to alloimmunization to HPA-3a. Materials and Methods: Platelet antibodies were detected by the monoclonal antibody-specific immobilization of platelet antigens, genotyping of the platelets by PCR, and HLA typing by serologic procedures and PCR. Results: Genotyping of maternal and paternal platelets confirmed the incompatibility in the HPA-3a system. It is noteworthy that the mother is of the HLA type DRB3*0101, is ABO-incompatible with her husband, and also has HLA class I antibodies. Conclusion: Severe neonatal thrombocytopenia associated with HPA-3a alloimmunization is infrequent and all the factors mentioned above could have played a role in the severity of the disease.     

Clinical relevance of gestational thrombocytopenia of <100,000/μl

We identified 22 women with thrombocytopenia of <100,000/μl found incidentally during pregnancy and prospectively monitored their platelet count and clinical outcome for a minimum of 6 months postpartum. During the study period, four women became pregnant twice, accounting for a total of 26 pregnancies. The lowest platelet count during pregnancy was 65,600/μl ± 19,400 (mean ± SD), and at delivery 84,500/μl ± 32,300 (P < 0.02). The thrombocytopenia was virtually asymptomatic in all patients during the pregnancy and delivery, whether vaginal or surgical. Neonatal platelet counts (n = 18) were normal (270,700/μl ± 69,900), and none of the newborns (n = 24) had a bleeding diathesis. Normalization of the platelet count (i.e., >150,000/μl) was documented in 18 patients within 1 month postpartum, in five within 3 months postpartum, and in two as late as 5 months after delivery. One woman did not recover from the thrombocytopenia and eventually developed other stigmata of an autoimmune disease. Long-term follow-up showed recurrence of thrombocytopenia in four patients: three in the context of a subsequent pregnancy and one who developed idiopathic thrombocytopenic purpura. Retrospective analysis of blood counts obtained from 12 previous pregnancies demonstrated thrombocytopenia of a similar degree to the index pregnancy. We conclude that gestational thrombocytopenia of <100,000/μl is clinically a benign phenomenon that can recur in subsequent pregnancies and is not accompanied by neonatal thrombocytopenia. In some cases, however, pregnancy-associated thrombocytopenia may be a manifestation of an autoimmune disease with its attendant implications for the neonate. Since the differential diagnosis between the two conditions may be difficult to establish when first encountered during pregnancy, a conservative approach emphasizing careful surveillance and guarded reassurance is justified as long as the platelet counts are >50,000/μl. © 1994 Wiley-Liss, Inc.     

Prevalence and Characterization of Thrombocytopenia in Pregnancy in Indian Women

To find the prevalence and causes of thrombocytopenia during pregnancy. An analytical prospective observational study was conducted in Department of Obstetrics & Gynecology, CSMMU, Lucknow. 1079 antenatal women screened for thrombocytopenia and investigated for cause and management strategies and fetomaternal outcome were recorded. Prevalence of thrombocytopenia was 8.8%. Gestational thrombocytopenia was seen in 64.2%, obstetric in 22.1% and medical in 13.68% cases. Mean platelet count in controls was lower with a significant fall (P < 0.001) in the platelet count as pregnancy advanced. Hypertensive and hepatic disorders were the most common obstetric causes of thrombocytopenia. Mode of delivery was not affected by thrombocytopenia. Maternal morbidity and mortality was seen only in medical and obstetric thrombocytopenia. The low platelet counts and declining trend with increasing gestational age predispose Indian women to risk of thrombocytopenia and a routine platelet count is suggested.