Alloimmune thrombocytopenia: fetal and neonatal losses related to cordocentesis

Assessing the applicability of obstetrical randomized controlled trials in real-world practices

This article examines the applicability of obstetrical randomized controlled trials (RCTs) in the real-world and proposes a classification of the value of these trials based on their potential for achieving sustainable practices. In the context of this discussion, real-world results pertain to the potential impact of the RCT on sustainable interventions and practices, and its implications for healthcare practice or policy, in the country (or countries) that was conducted. While RCTs are generally regarded as the gold standard of medical evidence, their effectiveness in producing meaningful real-world results depends, among various other factors, on the clarity and specificity of the trial definitions used for diagnosis (characteristics of the study group or enrollment criteria) and treatment (intervention). The definitions used for diagnosis and treatment, especially in pragmatic trials, can influence the likelihood for real-world implementation. By analyzing notable obstetrical RCTs, the authors find that trials with well-defined diagnoses and treatments that can be implemented without specialized expertise are more likely to generate results that are relevant to general practice, indicating higher value. In contrast, RCTs with ambiguous or undefined diagnoses and treatments often lead to variations in practice and produce unreliable real-world outcomes and practices suggesting lower value. Recognizing this variability can offer valuable guidance for the design and evaluation of RCTs in obstetrics.

Fetale und neonatale Alloimmunthrombozytopenie, Teil 2

Die fetale und neonatale Alloimmunthrombozytopenie (FNAIT) wird durch mütterliche Antikörper hervorgerufen, die gegen ein vom Vater ererbtes Blutgruppenmerkmal an fetalen Thrombozyten gerichtet sind. Während Teil 1 des Beitrags Ausgabe die Ätiologie, die Pathogenese und die Diagnostik der FNAIT thematisiert hatte, widmet sich dieser 2. Teil der Risikostratifizierung und Behandlung 1.

Prenatal Management of Pregnancies at Risk of Fetal Neonatal Alloimmune Thrombocytopenia (FNAIT): Scientific Impact Paper No. 61

WHAT IS IT?: Fetal neonatal alloimmune thrombocytopenia (FNAIT), also known as neonatal alloimmune thrombocytopenia (NAIT) or fetomaternal alloimmune thrombocytopenia (FMAIT), is a rare condition which affects a baby's platelets. This can put them at risk of problems with bleeding, particularly into the brain. One baby per week in the UK may be seriously affected and milder forms can affect one in every 1000 births. HOW IS IT CAUSED?: Platelets are blood cells that are very important in helping blood to clot. All platelets have natural proteins on their surface called human platelet antigens (HPAs). In babies, half of these antigens are inherited from the mother and half from the father. During pregnancy, some of the baby's platelets can cross into the mother's bloodstream. In most cases, this does not cause a problem. But in cases of FNAIT, the mother's immune system does not recognise the baby's HPAs that were inherited from the father and develops antibodies, which can cross the placenta and attack the baby's platelets. These antibodies are called anti-HPAs, and the commonest antibody implicated is anti-HPA-1a, but there are other rarer antibody types. If this happens, the baby's platelets may be destroyed causing their platelet count to fall dangerously low. If the platelet count is very low there is a risk to the baby of bleeding into their brain before they are born. This is very rare but if it happens it can have serious effects on the baby's health. HOW IS IT INHERITED?: A baby inherits half of their HPAs from its mother and half from its father. Consequently, a baby may have different HPAs from its mother. As the condition is very rare, and even if the baby is at risk of the condition we have no way of knowing how severely they will be affected, routine screening is not currently recommended. WHAT CAN BE DONE?: FNAIT is usually diagnosed if a previous baby has had a low platelet count. The parents are offered blood tests and the condition can be confirmed or ruled out. There are many other causes of low platelets in babies, which may also need to be tested for. As the condition is so rare, expertise is limited to specialist centres and normally a haematologist and fetal medicine doctor will perform and interpret the tests together. Fortunately, there is an effective treatment for the vast majority of cases called immunoglobulin, or IVIg. This 'blood product' is given intravenously through a drip every week to women at risk of the condition. It may be started from as early as 16 weeks in the next pregnancy, until birth, which would be offered at around 36-37 weeks. Less common treatments that may be considered depending on individual circumstances include steroid tablets or injections, or giving platelet transfusions to the baby. WHAT DOES THIS PAPER TELL YOU?: This paper considers the latest evidence in relation to treatment options in the management of pregnancies at risk of FNAIT. Specifically, we discuss the role of screening, when IVIg should be started, what dose should be used, and what evidence there is for maternal steroids. We also consider in very rare selected cases, the use of fetal blood sampling and giving platelet transfusions to the baby before birth. Finally, we consider the approaches to blood testing mothers to tell if babies are at risk, which is offered in some countries, and development of new treatments to reduce the risk of FNAIT.

Identification and follow-up of pregnant women with platelet-type human platelet antigen (HPA)-1bb alloimmunized with fetal HPA-1a

INTRODUCTION

Pregnant women negative for human platelet antigen 1a (HPA-1a) are at risk of alloimmunization with fetal HPA-1a antigen inherited from the father, and their offspring may develop fetal and neonatal alloimmune thrombocytopenia (FNAIT). The aim of this study was to analyze the frequency of HPA-1a alloimmunization in pregnant Polish women, the feasibility of using maternal platelets for intrauterine transfusions in women subjected to diagnostic fetal blood sampling (FBS) and to discuss potential consequences of alloimmunization.

MATERIAL AND METHODS

Fifteen thousand two hundred and four pregnant women were typed for HPA-1a; HPA-1a negative were screened for anti-HPA-1a. Alloimmunized women received specialist perinatology care; some of them were subjected to FBS, followed by transfusion of HPA-1a negative platelet concentrates (PC) prepared from maternal blood.

RESULTS

Three hundred seventy-three (2.5%) women were HPA-1a negative, and 32 (8.6%) tested positively for anti-HPA-1a. Antibodies were detected in 22 women during pregnancy. Diagnostic FBS followed by PC transfusion was performed in 14 woman, who were platelet donors for their 16 unborn babies. Blood donations were tolerated well by the patients, and also intrauterine platelet transfusions were uneventful. Pharmacotherapy with intravenous immunoglobulins was implemented in 11/22 patients.

CONCLUSIONS

HPA-1a negative women (ca. 2.5% of all pregnant patients) are at risk of alloimmunization with HPA-1a antigen and developing FNAIT. Alloimmunized women can be donors of platelets for their offspring providing removal of antibodies from PC. Owing to potential complications, special care should be taken if an alloimmunized woman was qualified as a blood or stem cell recipient.

Management and Neonatal Outcomes of Pregnancies with Fetal/Neonatal Alloimmune Thrombocytopenia: A Single-Center Retrospective Cohort Study

BACKGROUND

There is no consensus regarding the optimal antenatal treatment of fetal/neonatal alloimmune thrombocytopenia (F/NAIT). We aimed to review the fetal blood sampling (FBS)-related risk, fetal response to maternal intravenous immunoglobulin (IVIG), and cesarean section (CS) rate in pregnancies with a history of F/NAIT.

METHODS

Maternal demographics, alloantibodies, pregnancy management, fetal and neonatal outcomes, and index case characteristics were collected. Responders (R) and non-responders (NR) were defined as women treated with IVIG in whom fetal platelets (PLTs) were normal or low (< 50 × 109/L).

RESULTS

An FBS-related risk occurred in 1.6% (2/119) of procedures. Maternal characteristics did not differ between responders (n = 21) and non-responders (n = 21). HPA-1a antibody was detected in all non-responders and in 72% of responders (p < 0.01). The index case had a significantly lower PLT count at birth in non-responders versus responders (median PLT count: R = 20 × 109/L [IQR 8-43] vs. NR = 9 × 109/L [IQR 4-18], p < 0.02). No differences were found in IVIG treatment duration or dosage. PLTs at birth were significantly lower in non-responders compared to responders. No intracranial hemorrhages occurred. CSs were performed for obstetric indications only in all but two cases.

CONCLUSION

Maternal IVIG can elicit different fetal responses. The lack of prognostic factors to predict responders or non-responders suggests that there remains a role for FBS in F/NAIT in experienced hands.

Current perspectives on fetal and neonatal alloimmune thrombocytopenia - increasing clinical concerns and new treatment opportunities

Differences in platelet type between the fetus and the mother can lead to maternal immunization and destruction of the fetal platelets, a condition named fetal and neonatal alloimmune thrombocytopenia (FNAIT). FNAIT is reported to occur in ~1 per 1,000 live born neonates. The major risk is intracranial hemorrhage in the fetus or newborn, which is associated with severe neurological complications or death. Since no countries have yet implemented a screening program to detect pregnancies at risk, the diagnosis is typically established after the birth of a child with symptoms. Reports on broader clinical impact have increased clinical concern and awareness. Along with new treatment options for FNAIT, the debate around antenatal screening to detect pregnancies at risk of FNAIT has been revitalized.

Antenatal management in fetal and neonatal alloimmune thrombocytopenia: a systematic review

Several strategies can be used to manage fetal or neonatal alloimmune thrombocytopenia (FNAIT) in subsequent pregnancies. Serial fetal blood sampling (FBS) and intrauterine platelet transfusions (IUPT), as well as weekly maternal IV immunoglobulin infusion (IVIG), with or without additional corticosteroid therapy, are common options, but optimal management has not been determined. The aim of this systematic review was to assess antenatal treatment strategies for FNAIT. Four randomized controlled trials and 22 nonrandomized studies were included. Pooling of results was not possible due to considerable heterogeneity. Most studies found comparable outcomes regarding the occurrence of intracranial hemorrhage, regardless of the antenatal management strategy applied; FBS, IUPT, or IVIG with or without corticosteroids. There is no consistent evidence for the value of adding steroids to IVIG. FBS or IUPT resulted in a relatively high complication rate (consisting mainly of preterm emergency cesarean section) of 11% per treated pregnancy in all studies combined. Overall, noninvasive management in pregnant mothers who have had a previous neonate with FNAIT is effective without the relatively high rate of adverse outcomes seen with invasive strategies. This systematic review suggests that first-line antenatal management in FNAIT is weekly IVIG administration, with or without the addition of corticosteroids.

Fetal and Neonatal Alloimmune Thrombocytopenia: Management and Outcome of a Large International Retrospective Cohort

OBJECTIVE

To evaluate the management and outcome of a large international cohort of cases of pregnancies complicated by fetal and neonatal alloimmune thrombocytopenia (FNAIT).

METHODS

This was an observational prospective and retrospective cohort study of all cases of FNAIT entered into the international multicentre No IntraCranial Haemorrhage (NOICH) registry during the period of 2001-2010. We evaluated human platelet antigen (HPA) specificity, the antenatal and postnatal interventions performed, and clinical outcome.

RESULTS

A total of 615 pregnancies complicated by FNAIT from 10 countries were included. Anti-HPA-1a was the most commonly implicated antibody. Antenatal treatment was administered in 273 pregnancies (44%), varying from intrauterine platelet transfusion to maternal administration of immunoglobulins, steroids, or a combination of those. Intracranial haemorrhage was diagnosed in 23 fetuses or neonates (3.7%). Overall perinatal mortality was 1.14% (n = 7).

CONCLUSION

This study presents the largest cohort of cases of FNAIT published. Our data show that antenatal treatment for FNAIT results in favourable perinatal outcome. Over time, in most centres, treatment for FNAIT changed from an invasive to a complete non-invasive procedure.

Omission of fetal sampling in treatment of subsequent pregnancies in fetal-neonatal alloimmune thrombocytopenia

BACKGROUND

Fetal-neonatal alloimmune thrombocytopenia affects approximately 1 of 1000 live births, most of which are not severely thrombocytopenic. Despite effective treatment with intravenous gammaglobulin and/or prednisone, antenatal management of a subsequent affected pregnancy is complicated by the risks associated with fetal blood sampling. Furthermore, there are no biomarker(s) of high risk other than the occurrence of intracranial hemorrhage in a previous sibling. Management of these high-risk pregnancies requires intensive treatment initiated at 12 weeks of gestation.

OBJECTIVE

The objective of the study was to evaluate whether empiric escalation of therapy at 32 weeks allows the omission of fetal blood sampling in all fetal-neonatal alloimmune thrombocytopenia-affected patients. Specifically, we sought to determine whether intensive intravenous gammaglobulin-based regimens for the treatment of a subsequent fetal-neonatal alloimmune thrombocytopenia-affected pregnancy followed by empirically escalated intravenous gammaglobulin and prednisone treatment would increase the fetal platelet count and thus safely allow omission of fetal blood sampling in the antepartum management of these patients.

STUDY DESIGN

In this prospective, multicenter, randomized controlled study, 99 women with fetal-neonatal alloimmune thrombocytopenia whose prior affected child did not have an intracranial hemorrhage were randomized to receive an intensive intravenous gammaglobulin-based regimen: 2 g/kg per week or intravenous gammaglobulin 1 g/kg per week plus prednisone 0.5 mg/kg per day, starting at 20-30 weeks of gestation. Escalated therapy (intravenous gammaglobulin 2 g/kg per week plus prednisone 0.5 mg/kg per day) was recommended and usually initiated at 32 weeks when fetal counts were <50,000/mL(3) or when fetal blood sampling was not performed. The preliminary report of this study from 2007 demonstrated the efficacy of both intravenous gammaglobulin-based regimens in most patients. Most patients who underwent fetal sampling had adequate fetal counts and therefore did not have their treatment escalated. This post hoc analysis describes the 29 fetuses who had their treatment escalated either because they had low counts at 32 weeks or when sampling was not performed. This study explored whether the empiric escalation of treatment at 32 weeks was sufficiently effective in increasing fetal platelet counts in these patients.

RESULTS

Mean fetal and birth counts of fetuses randomized to each of the 2 initial treatment groups were all >100,000/mL(3). Three neonates had an intracranial hemorrhage; all 3 were grade 1 and all had birth platelet counts >130,000/mL(3). In a post hoc analysis, 19 fetuses undergoing fetal blood sampling at 32 weeks had fetal platelet counts <50,000/mL(3) despite their initial treatment. Of these 19, birth platelet counts were >50,000/mL(3) in 11 of 13 fetuses who received escalated treatment compared with only 1 of 6 of those who did not (P = .01); only 3 fetuses that received initial therapy followed by escalated treatment had birth platelet counts <50,000/mL(3) and none had an intracranial hemorrhage. The platelet counts of 14 of 15 fetuses that received empirically escalated treatment without sampling were >50,000/mL(3) at birth. In addition, none of these had an intracranial hemorrhage.

CONCLUSION

The 2 recommended protocols of intensive initial treatment followed by empiric escalation of therapy at 32 weeks of gestation are reasonably safe, effective in increasing fetal platelet counts, and allow omission of fetal blood sampling by increasing the fetal platelet count in almost all cases.

Platelets and platelet alloantigens: Lessons from human patients and animal models of fetal and neonatal alloimmune thrombocytopenia

Platelets play critical roles in hemostasis and thrombosis. Emerging evidence indicates that they are versatile cells and also involved in many other physiological processes and disease states. Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a life threatening bleeding disorder caused by fetal platelet destruction by maternal alloantibodies developed during pregnancy. Gene polymorphisms cause platelet surface protein incompatibilities between mother and fetus, and ultimately lead to maternal alloimmunization. FNAIT is the most common cause of intracranial hemorrhage in full-term infants and can also lead to intrauterine growth retardation and miscarriage. Proper diagnosis, prevention and treatment of FNAIT is challenging due to insufficient knowledge of the disease and a lack of routine screening as well as its frequent occurrence in first pregnancies. Given the ethical difficulties in performing basic research on human fetuses and neonates, animal models are essential to improve our understanding of the pathogenesis and treatment of FNAIT. The aim of this review is to provide an overview on platelets, hemostasis and thrombocytopenia with a focus on the advancements made in FNAIT by utilizing animal models.

Predicting risk severity and response of fetal neonatal alloimmune thrombocytopenia

Fetal neonatal alloimmune thrombocytopenia (FNAIT) is a devastating bleeding disorder in the fetus or neonate caused by transplacental transport of maternal alloantibodies to paternal-derived antigen on fetal platelets. In Caucasians, up to 80% of FNAIT cases result from maternal immunization to human platelet antigen (HPA)-1a. New methods have developed facilitating detection of common and private antibodies against HPAs triggering FNAIT. Understanding the pathogenesis of FNAIT made it possible to develop a novel strategy to treat this disorder. To date, recombinant monoclonal antibodies directed against the β3 integrin and Fc receptors have been tested in a mouse model of FNAIT, and seem to be promising. Whether those novel treatments will eventually replace the conventional high dose immunoglobulin G in women with FNAIT is yet unknown.

Neonatal alloimmune thrombocytopenia: pathogenesis, diagnosis and management

Neonatal alloimmune thrombocytopenia, (NAIT) is caused by maternal antibodies raised against alloantigens carried on fetal platelets. Although many cases are mild, NAIT is a significant cause of morbidity and mortality in newborns and is the most common cause of intracranial haemorrhage in full-term infants. In this report, we review the pathogenesis, clinical presentation, laboratory diagnosis and prenatal and post-natal management of NAIT and highlight areas of controversy that deserve the attention of clinical and laboratory investigators.

Antenatal interventions for fetomaternal alloimmune thrombocytopenia

BACKGROUND

Fetomaternal alloimmune thrombocytopenia results from the formation of antibodies by the mother which are directed against a fetal platelet alloantigen inherited from the father. The resulting fetal thrombocytopenia (reduced platelet numbers) may cause bleeding, particularly into the brain, before or shortly after birth. Antenatal treatment of fetomaternal alloimmune thrombocytopenia includes the administration of intravenous immunoglobulin (IVIG) and/or corticosteroids to the mother to prevent severe fetal thrombocytopenia. IVIG and corticosteroids both have short-term and possibly long-term side effects. IVIG is also costly and optimal regimens need to be identified.

OBJECTIVES

To determine the optimal antenatal treatment of fetomaternal alloimmune thrombocytopenia to prevent fetal and neonatal haemorrhage and death.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (28 February 2011) and bibliographies of relevant publications and review articles.

SELECTION CRITERIA

Randomised controlled studies comparing any intervention with no treatment, or comparing any two interventions.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed eligibility, trial quality and extracted data.

MAIN RESULTS

We included four trials involving 206 people. One trial involving 39 people compared a corticosteroid (prednisone) versus IVIG alone. In this trial, where analysable data were available, there was no statistically significant differences between the treatment arms for predefined outcomes. Three trials involving 167 people compared IVIG plus a corticosteroid (prednisone in two trials and dexamethasone in one trial) versus IVIG alone. In these trials there was no statistically significant difference in the findings between the treatment arms for predefined outcomes (intracranial haemorrhage; platelet count at birth and preterm birth). Lack of complete data sets and important differences in interventions precluded the pooling of data from these trials.

AUTHORS' CONCLUSIONS

The optimal management of fetomaternal alloimmune thrombocytopenia remains unclear. Lack of complete data sets for two trials and differences in interventions precluded the pooling of data from these trials which may have enabled a more developed analysis of the trial findings. Further trials would be required to determine optimal treatment (the specific medication and its dose and schedule). Such studies should include long-term follow up of all children and mothers.

A review of pathophysiology and current treatment for neonatal alloimmune thrombocytopenia (NAIT) and introducing the Australian NAIT registry

Fetomaternal or neonatal alloimmune thrombocytopenia (NAIT) is a rare but serious condition associated with significant fetal and neonatal morbidity and mortality. The most useful predictor of severe disease is a history of a sibling with an antenatal intracranial haemorrhage. However, NAIT can occur during the first pregnancy and may not be diagnosed until the neonatal period. Antenatal treatment options include maternal intravenous immunoglobulin (IVIG) and corticosteroid treatment, fetal blood sampling (FBS) and intrauterine platelet transfusion (IUT) and early delivery. FBS (with or without IUT) can be used to direct and monitor response to therapy, and to inform mode and timing of delivery. However, this procedure is associated with significant risks, including fetal death, and is generally now reserved for high-risk pregnancies. This review highlights the current understanding of the epidemiology and pathophysiology of NAIT and summarises current approaches to investigation and management. It also introduces the newly established Australian NAIT registry. Owing to the relative rarity of NAIT, accruing sufficient patient numbers for studies and clinical trials at an institutional level is difficult. This national registry will provide an opportunity to collect valuable information and inform future research on this condition.

Intracranial hemorrhage in alloimmune thrombocytopenia: stratified management to prevent recurrence in the subsequent affected fetus

OBJECTIVE

We sought to prevent intracranial hemorrhage (ICH) through antenatal management of alloimmune thrombocytopenia.

STUDY DESIGN

A total of 33 women (37 pregnancies) with alloimmune thrombocytopenia and ICH in a previous child were stratified according to the timing of the previous child's ICH: extremely high risk (HR) (n = 8) had ICH <28 weeks, very HR (n = 17) between 28-36 weeks, and HR (n = 12) in the perinatal period. Treatment was initiated at 12 weeks with intravenous immunoglobulin 1 or 2 g/kg/wk, and if the fetal platelet count by cordocentesis was <30,000/mL despite treatment, prednisone and/or more intravenous immunoglobulin were added.

RESULTS

Five of 37 fetuses suffered ICHs. Two ICHs had platelet counts >100,000/mL, and 1 was grade I. The other 2 ICHs were unequivocal treatment failures; both were grade III-IV and resulted in fetal demise.

CONCLUSION

These findings demonstrate the success of stratified treatment in these HR patients, which tailored interventions according to the timing of the sibling's ICH.

Management of fetal alloimmune thrombocytopenia-a less invasive option?

Fetal alloimmune thrombocytopenia (FAITP) is a condition associated with significant infant morbidity and mortality. We report on the West of Scotland experience of 30 pregnancies complicated by FAITP over a 17-year period (1982-98). Management options included serial cordocentesis together with platelet transfusion, and maternal intravenous gammaglobulin (IVIgG) therapy. Of those pregnancies managed by serial cordocentesis all had poor outcomes. Weekly IVIgG was administered to the remaining pregnancies, all of which had a good outcome although four infants were thrombocytopenic at birth. None of these cases had previously been complicated by intracranial haemorrhage. In the milder end of the spectrum of FAITP we would suggest that IVIgG is an alternative treatment option.

Diagnosis and management of the fetus and neonate with alloimmune thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia (AIT) is the commonest cause of severe thrombocytopenia in neonates, and of intracranial hemorrhage (ICH) in term neonates [1] (J Trop Pediatr, 1999; 45: 237). If a newborn is affected with AIT, the next child will likely be more severely affected, and therefore fetal thrombocytopenia will begin early in gestation [2, 3] (Arch Neurol, 1984; 41: 30; N Engl J Med 1997; 337: 22). This creates a risk of in utero ICH even if there was not one in the previous pregnancy. There are new developments in AIT in regard to diagnosis, treatment, and screening which will be the focus of this review.

Evidence for the specificity for platelet HPA-1a alloepitope and the presenting HLA-DR52a of diverse antigen-specific helper T cell clones from alloimmunized mothers

Maternal alloantibodies against the human platelet Ag (HPA)-1a allotype of the platelet beta(3) integrin GpIIb/IIIa can cause severe fetal or neonatal hemorrhage. Almost all anti-HPA-1a-immune mothers are homozygous for HPA-1b and carry HLA-DR52a (DRB3*0101). The single Pro(33) -->Leu substitution (HPA-1b-->HPA-1a) was previously predicted to create a binding motif for HLA-DR52a that can lead to alloimmunization. We have isolated six CD4(+) T cell clones from three such mothers, which all respond to intact HPA-1a(+), but not HPA-1b(+), platelets. We used them to define the "core" and "anchor" residues of this natural T cell epitope. Molecular modeling based on a recently published crystal structure can explain the preferential presentation of the Leu(33) (but not Pro(33) variant) by HLA-DR52a rather than the linked HLA-DR3 or the allelic DR52b. The modeling also predicts efficient anchoring at position 33 by several alternative hydrophobic alpha-amino acids; indeed, a recently identified variant with Val(33) is presented well to two clones, and is therefore potentially alloimmunogenic. Finally, these HPA-1a-specific T cell clones use a variety of T cell receptors, but all have a "Th1" (IFN-gamma-producing) profile and are suitable for testing selective immunotherapies that might be applicable in vivo.

Current approaches to the evaluation and management of the fetus and neonate with immune thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia is not a well-known disease, except among specialists in maternal-fetal medicine, neonatologists, and certain pediatricians (ie, hematologists). However, this is by far the most common cause of early severe thrombocytopenia in neonates and of intracranial hemorrhage in term neonates. In addition, if a newborn is affected with alloimmune thrombocytopenia, the next child in the family will likely be more severely affected. Thus, the accurate diagnosis and appropriate management of this disorder are of extreme importance in perinatal medicine and will constitute the focus of this review.

Developing recombinant HPA-1a-specific antibodies with abrogated Fcgamma receptor binding for the treatment of fetomaternal alloimmune thrombocytopenia

Fetomaternal alloimmune thrombocytopenia (FMAIT) is caused by maternal generation of antibodies specific for paternal platelet antigens and can lead to fetal intracranial hemorrhage. A SNP in the gene encoding integrin beta3 causes a clinically important maternal-paternal antigenic difference; Leu33 generates the human platelet antigen 1a (HPA-1a), whereas Pro33 generates HPA-1b. As a potential treatment to prevent fetal intracranial hemorrhage in HPA-1a alloimmunized pregnancies, we generated an antibody that blocks the binding of maternal HPA-1a-specific antibodies to fetal HPA-1a1b platelets by combining a high-affinity human HPA-1a-specific scFv (B2) with an IgG1 constant region modified to minimize Fcgamma receptor-dependent platelet destruction (G1Deltanab). B2G1Deltanab saturated HPA-1a+ platelets and substantially inhibited binding of clinical HPA-1a-specific sera to HPA-1a+ platelets. The response of monocytes to B2G1Deltanab-sensitized platelets was substantially less than their response to unmodified B2G1, as measured by chemiluminescence. In addition, B2G1Deltanab inhibited chemiluminescence induced by B2G1 and HPA-1a-specific sera. In a chimeric mouse model, B2G1 and polyclonal Ig preparations from clinical HPA-1a-specific sera reduced circulating HPA-1a+ platelets, concomitant with transient thrombocytopenia. As the Deltanab constant region is uninformative in mice, F(ab')2 B2G1 was used as a proof of principle blocking antibody and prevented the in vivo platelet destruction seen with B2G1 and polyclonal HPA-1a-specific antibodies. These results provide rationale for human clinical studies.

Intrahepatic vein for fetal blood sampling: one center's experience

OBJECTIVE

The objective of the study was to examine 1 center's experience with fetal blood sampling via the fetal intrahepatic vein (IHV) and cordocentesis.

STUDY DESIGN

Consecutive IHV and cordocentesis procedures between July 1987 and February 2006 were compared with respect to success rates, streaming at the sampling site, nonreassuring fetal heart rate (NRFHR), or need for urgent delivery post procedure. A subanalysis of cases with fetal thrombocytopenia was performed. Data were analyzed using Fisher's exact and Student t tests.

RESULTS

Two hundred ten procedures (130 IHV samplings and 110 cordocenteses) were identified. Success rates were significantly higher with IHV sampling than with cordocentesis (84.6% vs 69.1%, P = .004). Streaming from the sampling site occurred after 0.79% of IHV procedures vs 30.8% of cordocenteses (P < .0001). There was no difference between IHV and cordocentesis in the incidence of NRFHR or need for immediate delivery. Twenty-five cases of fetal thrombocytopenia (20 sampled via IHV, 5 by cordocentesis) were identified. Streaming from the sampling site occurred in 0 of 20 IHV cases vs 2 of 5 cordocentesis cases (40%) (P = .03).

CONCLUSION

IHV has a significantly lower rate of streaming from the sampling site, compared with cordocentesis. Our data suggest that IHV sampling conveys a particular advantage when fetal thrombocytopenia is suspected.

Fetal and neonatal alloimmune thrombocytopenia: progress and ongoing debates

Fetal and neonatal alloimmune thrombocytopenia (AIT) is a result of a parental incompatibility of platelet-specific antigens and the transplacental passage of maternal alloantibodies against the platelet antigen shared by the father and the fetus. It occurs in approximately 1 in 1000 live births and is the most common cause of severe thrombocytopenia in fetuses and term neonates. As screening programs are not routinely performed, most affected fetuses are identified after birth when neonatal thrombocytopenia is recognized. In severe cases, the affected fetus is identified as a result of suffering from an in utero intracranial hemorrhage. Once diagnosed, AIT must be treated antenatally as the disease can be more severe in subsequent pregnancies. While there have been many advances regarding the diagnosis and treatment of AIT, it is still difficult to predict the severity of disease and which therapy will be effective.

Antepartum treatment without early cordocentesis for standard-risk alloimmune thrombocytopenia: a randomized controlled trial

OBJECTIVE

To evaluate the effectiveness and safety of two antenatal treatment regimens designed to optimally protect fetuses against intracranial hemorrhage resulting from alloimmune thrombocytopenia while minimizing the risks associated with fetal blood sampling. The study was limited to "standard-risk" patients, who were defined as women with documented alloimmune thrombocytopenia who had not delivered an infant with an intracranial hemorrhage in a prior pregnancy.

METHODS

In this prospective multicenter study of 73 women with documented alloimmune thrombocytopenia, patients were randomized to receive either intravenous immunoglobulin (IVIG) 2 g/kg/wk (group A) or IVIG 1 g/kg/wk plus prednisone 0.5 mg/kg/d (group B), starting at approximately 20 weeks of gestation. Fetal blood sampling was performed at approximately 32 weeks of gestation, and those with fetal platelet counts less than 30,000/mL(3) were given salvage therapy.

RESULTS

There were two intracranial hemorrhages; neither was due to treatment failure. The average platelet counts at the time of fetal blood sampling were 121,600/mL(3) and 116,100/mL(3), and the average birth platelet counts were 169,400/mL(3) and 134,000/mL(3) for groups A and B, respectively. Twenty-seven percent of patients in group A and 17% in group B received salvage therapy, and only one neonate in each of these subsets had a birth platelet count less than 30,000/mL(3). There were four complications after 79 fetal blood sampling procedures, leading to cesarean deliveries between 32 and 37 weeks. There was a higher incidence of gestational diabetes and a tendency to more fluid retention, mood swings, insomnia, and jitteriness in patients on prednisone and of moderate-to-severe fatigue in those on high-dose IVIG alone.

CONCLUSION

The outcomes of both treatment groups were excellent and comparable. Early cordocentesis is not necessary when treating alloimmune thrombocytopenia in patients who have not delivered an infant with an intracranial hemorrhage in a prior pregnancy.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, www.clinicaltrials.gov, NCT00194987

LEVEL OF EVIDENCE

I.

HPA-1a antibody potency and bioactivity do not predict severity of fetomaternal alloimmune thrombocytopenia

BACKGROUND

The antenatal management of fetomaternal alloimmune thrombocytopenia (FMAIT) due to HPA-1a antibodies remains controversial, and a test identifying pregnancies that do not require therapy would be of clinical value.

STUDY DESIGN AND METHODS

The statistical correlation was analyzed between clinical outcome and 1) anti-HPA-1a potency in maternal serum samples determined by a monoclonal antibody immobilization of platelet (PLT) antigen assay with an international anti-HPA-1a potency standard and 2) anti-HPA-1a biological activity measured by a monocyte chemiluminescence (CL) assay.

RESULTS

A total of 133 pregnancies with FMAIT due to anti-HPA-1a were analyzed. In 97 newly diagnosed cases, there was no difference in antibody potency or CL signal between cases with intracranial hemorrhage (ICH; n = 15), those with no ICH but a PLT count of less than 20 x 10(9) per L (n = 52), and those with a PLT count of at least 20 x 10(9) per L (n = 30). In 22 previously known pregnancies, the positive predictive value of maternal anti-HPA-1a of greater than 30 IU per mL for a PLT count of less than 20 x 10(9) per L was 90 percent, but the negative predictive value was only 66 percent. Antibody potency tended to stay stable throughout pregnancy (n = 16) and from one pregnancy to the next (n = 16).

CONCLUSION

Neither severe thrombocytopenia nor ICH in HPA-1a-alloimmunized pregnancies can be predicted with sufficient sensitivity and specificity for clinical application from maternal anti-HPA-1a potency or bioactivity.

Noninvasive antenatal management of fetal and neonatal alloimmune thrombocytopenia: safe and effective

OBJECTIVE

To describe the outcome of pregnancies with fetal and neonatal alloimmune thrombocytopenia (FNAIT) in relation to the invasiveness of the management protocol.

DESIGN

Retrospective analysis of prospectively collected data from a national cohort.

SETTING

Leiden University Medical Centre, the national centre for management of severe red cell and platelet alloimmunisation in pregnancy.

POPULATION

Ninety-eight pregnancies in 85 women with FNAIT having a previous child with thrombocytopenia with (n= 16) or without (n= 82) an intracranial haemorrhage (ICH).

METHODS

Our management protocol evolved over time from (1) serial fetal blood samplings (FBS) and platelet transfusion (n= 13) via (2) combined FBS with maternal intravenous immunoglobulins (n= 33) to (3) completely noninvasive treatment with immunoglobulins only (n= 52 pregnancies, resulting in 53 neonates). Perinatal outcome was assessed according to the three types of management.

MAIN OUTCOME MEASURES

Occurrence of ICH, perinatal survival, gestational age at birth and complications of FBS.

RESULTS

All but one of 98 pregnancies ended in a live birth; none of the neonates had an ICH. The median gestational age at birth was 37 weeks (range 32-40). In groups 1 and 2, three emergency caesarean sections were performed after complicated FBS, resulting in two healthy babies and one neonatal death.

CONCLUSION

Noninvasive antenatal management of pregnancies complicated by FNAIT appears to be both effective and safe.

Advances in the management of alloimmune thrombocytopenia

There have been considerable advances in the clinical and laboratory diagnosis of alloimmune thrombocytopenia (AIT), and its postnatal and antenatal management. The antenatal management of AIT has been particularly problematic, because severe haemorrhage occurs as early as 16 weeks gestation and there is no non-invasive investigation that reliably predicts the severity of AIT in utero. The strategies for antenatal treatment have included the use of serial platelet transfusions that, while effective, are invasive and associated with significant morbidity and mortality. Maternal therapy involving the administration of intravenous immunoglobulin and/or steroids is also effective and associated with fewer risks to the fetus. Significant recent progress has involved refinement of maternal treatment, stratifying it according to the likely severity of AIT based on the history in previous pregnancies. However, the ideal antenatal treatment, which is effective without causing significant side-effects to the mother or fetus, has yet to be determined, and further clinical trials are needed.

[Is a non-invasive management allowed for maternofetal alloimmune thrombocytopenia? Experience over a 10-year period]

OBJECTIVES

Our purpose was to study a non-invasive management of fetomaternal alloimmune thrombocytopenia (FMAIT).

PATIENTS AND METHODS

Between 1996 and 2005, 18 women were treated. The population was divided into 2 groups: patients with a history of intracranial haemorrhage (ICH) in the older sibling received weekly intravenous immunoglobulin (IVIG) therapy to the mother (1 g/kg per week) without initial cordocentesis whereas patients with a history of neonatal thrombocytopenia did not undergo any treatment.

RESULTS

All pregnancies with a previous FMAIT were monitored with serial ultrasound scans without cordecentesis. 15 patients had HPA-1, 2 HPA-3 and 1 HPA-5 immunizations. Weekly intravenous immunoglobulin therapy was administered in 5 patients with a history of ICH in the older sibling. Two of these delivered thrombocytopenic children; one had a platelet count < 50 x 10(9)/l. For the 13 women (one twin) who had a sibling with neonatal thrombocytopenia, 11/14 newborns had a platelet count < 50 x 10(9)/l. Predelivery fetal blood sampling were performed in 8/18 pregnancies. The neonatal periods of the 19 children were uncomplicated and no ICHs were observed.

DISCUSSION AND CONCLUSION

Our results suggest that a non-invasive strategy avoiding serial cordocentesis may be an effective therapy in patients who are at risk of fetal and neonatal alloimmune thrombocytopenia.

Fetal thrombocytopenia secondary to parvovirus infection

OBJECTIVE

The aim of this study was to determine the platelet count in fetuses undergoing cordocentesis for hydrops caused by parvovirus infection.

STUDY DESIGN

Fetal platelets were measured at cordocentesis in 11 pregnant women who underwent the procedure because of fetal ascites and/or hydrops caused by parvovirus infection. Thrombocytopenia was defined as mild (platelet count < 150 x 10(9)/L), moderate (platelet count < or = 100 x 10(9)/L), or severe (platelet count to < or = 50 x 10(9)/L). Paired Student t test was performed to compare the platelet count before and after the transfusion.

RESULTS

The fetuses underwent 20 cordocenteses. They were thrombocytopenic in 17 and anemic in 15 occasions. The platelet count was reduced after the transfusion (P < .05). Demises occurred after the first transfusion in 2 fetuses. The first occurred within 5 minutes from the procedure and the second within 24 hours. Both were attributed to exsanguination from the umbilical cord puncture site (platelet count 2 and 24 x 10(9)/L, respectively).

CONCLUSION

Thrombocytopenia is common in fetuses with hydrops caused by parvovirus infection, and can cause exsanguination from the umbilical cord puncture site. We recommend platelet transfusion during cordocentesis when there is severe thrombocytopenia.

Alloimmune thrombocytopenia: state of the art 2006

In alloimmune thrombocytopenia maternal immunoglobulin G anti-platelet alloantibodies cross the placenta and cause fetal thrombocytopenia. The diagnosis requires laboratory demonstration of incompatibility between a maternal and paternal platelet alloantigen, and detection of maternal antibody to the discordant paternal alloantigen. This disorder should be treated in utero because of its propensity to cause fetal intracranial bleeding. Administration of intravenous immunoglobulin 1 gm/kg/wk to the mother is successful in substantially raising the platelet count in many fetuses, but this is most successful if the count is >20,000/mL3 at the time that the therapy is initiated. The addition of prednisone administered daily to the mother and/or increasing the dose of intravenous immunoglobulin has a therapeutic benefit in cases that have failed to respond to initial therapy with intravenous immunoglobulin alone. The only reliable noninvasive indicator of the potential for severe fetal thrombocytopenia is a history of an antenatal intracranial hemorrhage in a prior affected sibling. Because fetal blood sampling to determine the fetal platelet count may be associated with significant fetal morbidity, attempts are being made to derive a rational, non-invasive, stratified approach to patient-specific therapy of this disorder in affected pregnancies.

Antenatal noninvasive treatment of patients at risk for alloimmune thrombocytopenia without a history of intracranial hemorrhage

OBJECTIVE

The purpose of this study was to evaluate noninvasive management of alloimmune thrombocytopenia that included only the blind administration of immunoglobulin.

STUDY DESIGN

Seventeen women with 30 pregnancies that were at risk of neonatal alloimmune thrombocytopenia were included. Except for 6 cases, in which the women refused treatment, 24 pregnancies were managed by the weekly administration of intravenous immunoglobulin without monitoring platelet count.

RESULTS

The mean platelet count at birth after intravenous immunoglobulin treatment was 118,000/microL, compared with 25,000/microL among the 17 first affected infants and 24,000/microL among the 6 infants whose mothers refused treatment (P < .05). Only 8% of the treated fetuses had platelet counts of <30,000/microL at birth, compared with 70% of the untreated infants (P < .05). None of the treated and nontreated fetuses had an intracranial hemorrhage.

CONCLUSION

Noninvasive management of alloimmune thrombocytopenia that consists of only immunoglobulin administration is highly effective and seems safe in women without a history of fetal/neonatal intracranial hemorrhage.

Efficacy and safety of cordocentesis for prenatal diagnosis

OBJECTIVE

To assess the efficacy and safety of diagnostic cordocentesis.

METHODS

Between January 1991 and May 2004, 2,010 cordocentesis were performed in the outpatient setting in 2,010 women with singleton pregnancies. A fixed needle guide and a 22-gauge percutaneous needle were used and no more than 2 attempts were allowed at 1 visit. In most cases, the umbilical vein was the target vessel. The results of each procedure and pregnancy outcomes were recorded and analyzed.

RESULTS

The most frequent indication for cordocentesis was risk of severe thalassemia (59.0%), followed by a need for rapid karyotyping (30.0%). Most of the procedures (97%) were performed in the free cord loop and the remaining at the cord insertion. The overall success rate was 98.4%, with 80.0% of the successful procedures performed at the first needle insertion and the remaining 20% at the second insertion. Transient bleeding was observed at the puncture site in 19.8% of cases and transient fetal bradycardia in 4.9% of cases. The total fetal loss and cordocentesis-related loss rates within 2 weeks of cordocentesis were 2.7% and 1.0%, respectively, before 24 weeks of gestation and 1.9% and 0.8% after 24 weeks. The other obstetric complications were unremarkable.

CONCLUSIONS

Cordocentesis is a simple, safe, and reliable procedure for prenatal diagnosis.

Predictive value of sequential maternal anti-HPA-1a antibody concentrations for the severity of fetal alloimmune thrombocytopenia

BACKGROUND

Fetal/neonatal alloimmune thrombocytopenia results from maternal immunization against fetal platelet alloantigens (HPAs), and the major risk is intracranial hemorrhage. The severity of thrombocytopenia increases in subsequent pregnancies, and antenatal therapy has been developed. Until now, the fetal status can only be assessed by fetal blood sampling, which carries a risk of fetal loss or premature delivery.

OBJECTIVES

To develop non-invasive methods to gain information on the fetal condition.

PATIENTS/METHODS

Quantification of the maternal anti-HPA-1a alloantibody concentration was performed with a standardized monoclonal antibody-specific immobilization of platelet antigens (MAIPA) procedure for 43 mothers. A correlation between this concentration and the fetal/neonatal platelet counts was studied.

RESULTS

(i) Before antenatal therapy, there was a significant correlation between maternal anti-HPA-1a concentrations > or =250 AU mL(-1) and fetal thrombocytopenia (2-66 x 10(9) L(-1)) whatever the gestational age (Fisher's exact test P = 0.0021). (ii) During subsequent pregnancies, we observed a decrease of the maternal anti-HPA-1a concentration for 14/19 women. Just before delivery, all women had anti-HPA-1a concentrations <250 AU mL(-1). In four cases, there was a therapy failure and the severely thrombocytopenic babies required postnatal therapy.

CONCLUSION

The maternal anti-HPA-1a concentration could provide obstetricians with clinically useful information concerning the appropriateness and the timing of invasive monitoring procedures. However, though we observed a tendency toward a decrease in maternal antibody concentration after treatment, this finding does not allow us to draw any conclusions on the effectiveness of therapy.

Parallel Randomized Trials of Risk-Based Therapy for Fetal Alloimmune Thrombocytopenia

OBJECTIVE

Antenatal therapy with intravenous immunoglobulin (IVIG) and prednisone has been shown to improve fetal thrombocytopenia and reduce the incidence of intracranial hemorrhage in neonatal alloimmune thrombocytopenia. Optimization of this therapy for individual patients, however, has yet to be achieved.

METHODS

In these parallel, randomized, multicenter studies, 78 patients in 79 pregnancies were stratified to 2 different treatment arms based on the presence of a peripartum intracranial hemorrhage in a previously affected sibling and/or the initial fetal platelet count. Patients with a history of an antenatal intracranial hemorrhage in a prior pregnancy were excluded.

RESULTS

Forty women whose children from a previous birth had a peripartum intracranial hemorrhage or whose current fetus had an initial platelet count less than 20,000/mL3 were randomly assigned to receive IVIG plus prednisone or IVIG alone. The mean increase in fetal platelet counts in the following 3 to 8 weeks was 67,100/mL3 and 17,300/mL3, respectively (P < .001). Thirty-nine patients whose prior affected child did not have an intracranial hemorrhage and whose initial platelet count was more than 20,000/mL3 were randomly assigned to receive IVIG alone or prednisone alone. There were no significant differences, and 33 (85%) had birth platelet counts more than 50,000/mL3. There were 11 (6%) significant complications after a total of 175 fetal blood sampling procedures, 2 of which led to fetal or neonatal deaths.

CONCLUSION

The spectrum of disease severity of alloimmune thrombocytopenia is reflected in the initial fetal platelet count and response to therapy. Fetal blood sampling may be associated with significant fetal/neonatal morbidity and mortality. Empiric therapy sufficient to treat the most severely affected fetuses will overtreat others and is likely to be associated with additional maternal morbidity.

Intravenous Immunoglobulins without Initial and Follow-Up Cordocentesis in Alloimmune Fetal and Neonatal Thrombocytopenia at High Risk for Intracranial Hemorrhage

OBJECTIVE

To report on a less invasive treatment strategy in alloimmune fetal and neonatal thrombocytopenia (FNAIT) at high risk for either in utero or neonatal intracranial hemorrhage (ICH).

METHODS

In 7 pregnancies, with a history of ICH in the older sibling, weekly intravenous immunoglobulin (IVIG) therapy to the mother (1 g/kg) without initial cordocentesis was started at a median gestational age of 16 weeks.

RESULTS

In 4 pregnancies cordocentesis was avoided. One predelivery cordocentesis with platelet transfusion was performed in 3 further cases. Although none of the cases had a platelet count of >50 x 10(9)/l at cordocentesis, predelivery or birth, no ICHs were observed. The neonatal periods of the infants were uncomplicated.

CONCLUSION

IVIG treatment alone might be considered in patients with both severe platelet alloimmunization and an increased risk for morbidity and mortality at cordocentesis.

The cost effectiveness of empiric intravenous immunoglobulin for the antepartum treatment of fetal and neonatal alloimmune thrombocytopenia

OBJECTIVE

The purpose of this study was to compare the cost effectiveness of empiric intravenous immunoglobulin (IVIG) with that of fetal blood sampling-indicated treatment for the antepartum care of fetal and neonatal alloimmune thrombocytopenia.

STUDY DESIGN

We developed a decision analysis model to compare the cost effectiveness of 2 strategies for treatment of pregnancies in women with a history of fetal and neonatal alloimmune thrombocytopenia and an at-risk fetus: 1) IVIG and corticosteroids as indicated by fetal platelet levels determined by fetal blood sampling (FBS); and 2) empiric IVIG. In the first strategy, FBS is used to measure fetal platelets at 24 weeks of gestation and repeated 6 weeks later to guide pharmacotherapy. In the second strategy, weekly IVIG is empirically administered from 24 weeks' to 37 weeks' gestation. The main outcome measure was the marginal cost per quality-adjusted life years (QALY) gained.

RESULTS

For every 1000 women with a fetus at risk for recurrent alloimmune thrombocytopenia, empiric therapy, compared with FBS-indicated treatment, decreases perinatal deaths from 31.7 to 11.8 while increasing the number of infants with long-term neurologic deficits from 6.1 to 9.6. These health outcomes translate to 382 QALYs gained with empiric therapy and a cost effectiveness ratio of dollar 32,747 per QALY favoring empiric therapy. In the sensitivity analysis, empiric therapy was not cost effective when the rate of perinatal ICH exceeded 28%.

CONCLUSION

Empiric IVIG therapy is a cost-effective strategy for the treatment of women at risk for fetal and neonatal alloimmune thrombocytopenia when the rate of perinatal ICH is less than 28%.