Serial aggressive platelet transfusion for fetal alloimmune thrombocytopenia: platelet dynamics and perinatal outcome

How do we perform intrauterine transfusions?

BACKGROUND

Intrauterine transfusion (IUT) is an invasive but critical and potentially life-saving intervention for severe fetal anemia with demonstrated improvement in outcomes. The fetus is vulnerable to hemodynamic alterations and transfusion-related adverse events; therefore, special consideration must be given to blood component selection and modification. There is widespread IUT practice variability, and existing guidance primarily relies on expert opinion and single center experiences.

STUDY DESIGN AND METHODS

Experts in Maternal Fetal Medicine, Pediatric Hematology, and Transfusion Medicine from centers across the United States, collectively performing about 120 IUT annually, offer a multidisciplinary perspective on the performance of IUT and preparation of blood components. This perspective includes strategies for identifying an at-risk fetus, communicating between disciplines, determining the necessary blood volume, selecting and processing blood components, documenting the procedure in medical record, and managing the neonate.

RESULTS

Identifying an at-risk fetus relies on review of the clinical history, non-invasive monitoring, and laboratory evaluation. We recommend the use of relatively fresh, group O, cytomegalovirus-safe, freshly irradiated, red blood cells (RBC) that are Hemoglobin S negative and antigen-negative for any maternal antibody, if indicated. These RBC units should be concentrated to remove additives and increase the hematocrit thus minimizing fluctuations in fetal volume status. The units intended for IUT should be labeled clearly and the documentation of transfusion differentiated in the maternal medical record.

DISCUSSION

An awareness of the technical, logistical, and regulatory considerations for IUT performance will facilitate improved communication and patient care, especially when rare units of RBC are required.

New Horizons in Fetal and Neonatal Alloimmune Thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a common cause of severe thrombocytopenia in newborns. Intracranial bleeding may lead to severe neurological sequelae and mortality. Current management of pregnancies at risk is suboptimal. Prenatal FNAIT diagnosis commonly requires invasive procedures and therapy is associated with a high treatment burden. The present review explores advances in the field and their potential contribution to modification of the diagnostic and therapeutic landscape. Topics addressed include the role of noninvasive prenatal testing using fetal cell free DNA, insights into novel and prospective therapeutic options achieved through the development of murine models of FNAIT as well as the forecast for the progress in pregnancy risk stratification through advancement in the investigation of biological characteristics of alloantibodies and their association with the risk of fetal bleeding.

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.

Non-invasive risk-assessment and bleeding prophylaxis with IVIG in pregnant women with a history of fetal and neonatal alloimmune thrombocytopenia: management to minimize adverse events

INTRODUCTION

In pregnant women with a history of fetal and neonatal alloimmune thrombocytopenia (FNAIT), prenatal intervention in subsequent pregnancies may be required to prevent fetal bleeding. Several invasive and non-invasive protocols have been published: amniocentesis for fetal genotyping, fetal blood sampling for the determination of fetal platelet count, intrauterine platelet transfusions, and weekly maternal i.v. immunoglobulin (IVIG) infusion with or without additional corticosteroid therapy. This is the first retrospective study that report the experience with a non-invasive protocol focused on side effects of maternal IVIG treatment and neonatal outcome.

METHODS

Pregnant women with proven FNAIT in history and an antigen positive fetus were treated with IVIG (1 g/kg/bw) every week. To identify potential IVIG-related hemolytic reactions isoagglutinin titer of each IVIG lot and maternal blood count were controlled. IVIG-related side effects were prospectively documented and evaluated. Furthermore, ultrasound examination of the fetus was performed before starting IVIG administration and continued regularly during treatment. Outcome of the index and subsequent pregnancy was compared. Corresponding data of the newborns were analyzed simultaneously.

RESULTS

IVIG was started at 20 weeks of gestation (median). Compared to the index pregnancy, platelet counts of the newborns were higher in all cases. No intracranial hemorrhage occurred (Index pregnancies: 1 case). Platelet counts were 187 × 10⁹/l (median, range 22-239, 95% CI) and one newborn had mild bleeding. No severe hemolytic reaction was observed and side effects were moderate.

CONCLUSION

Among pregnant women with FNAIT history, the use of non-invasive fetal risk determination and maternal IVIG resulted in favorite outcome of all newborns. Invasive diagnostic or therapeutic procedures in women with a history of FNAIT should be abandoned.

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.

Fetal/Neonatal Alloimmune Thrombocytopenia: Pathogenesis, Diagnostics and Prevention

Fetal/neonatal alloimmune thrombocytopenia (FNAIT) is a relatively rare condition (1/1000–1/2000) that was granted orphan status by the European Medicines Agency in 2011. Clinical consequences of FNAIT, however, may be severe. A thrombocytopenic fetus or new-born is at risk of intracranial hemorrhage that may result in lifelong disability or death. Preventing such bleeding is thus vital and requires a solution. Anti-HPA1a antibodies are the most frequent cause of FNAIT in Caucasians. Its pathogenesis is similar to hemolytic disease of the newborn (HDN) due to anti-RhD antibodies, but is characterized by platelet destruction and is more often observed in the first pregnancy. In 75 % of these women, alloimmunization by HPA-1a antigens, however, occurs at delivery, which enables development of antibody-mediated immune suppression to prevent maternal immunization. As for HDN, the recurrence rate of FNAIT is high. For advancing diagnostic efforts and treatment, it is thereby crucial to understand the pathogenesis of FNAIT, including cellular immunity involvement. This review presents the current knowledge on FNAIT. Also described is a program for HPA-1a screening in identifying HPA-1a negative pregnant women at risk of immunization. This program is now performed at the Institute of Hematology and Transfusion Medicine in cooperation with the Department of Obstetrics and Gynecology of the Medical Centre of Postgraduate Education in Warsaw as well as the UiT The Arctic University of Norway.

Fetal thrombocytopenia in pregnancies with fetal human parvovirus-B19 infection

OBJECTIVE

Fetal infection with human parvovirus B19 (hParvo-B19) has been associated mainly with fetal anemia, although data regarding other fetal hematologic effects are limited. Our aim was to assess the rate and consequences of severe fetal thrombocytopenia after fetal hParvo-B19 infection.

STUDY DESIGN

We conducted a retrospective study of pregnancies that were complicated by fetal hParvo-B19 infection that underwent fetal blood sampling (FBS). The characteristics and outcomes of fetuses with severe thrombocytopenia (<50 × 10(9)/L) were compared with those of fetuses with a platelet concentration of ≥50 × 10(9)/L (control fetuses). Fetuses in whom 3 FBSs were performed (n = 4) were analyzed to assess the natural history of platelet levels after fetal hParvo-B19 infection.

RESULTS

A total of 37 pregnancies that were affected by fetal hParvo-B19 infection were identified. Of the 29 cases that underwent FBS and had information regarding fetal platelets, 11 cases (38%) were complicated by severe fetal thrombocytopenia. Severely thrombocytopenic fetuses were characterized by a lower hemoglobin concentration (2.6 ± 0.9 g/dL vs 5.5 ± 3.6 g/dL; P = .01), lower reticulocyte count (9.1% ± 2.8% vs 17.3% ± 10.6%; P = .02), and lower gestational age at the time of diagnosis (21.4 ± 3.1 wk vs 23.6 ± 2.2 wk; P = .03). Both the fetal death rate within 48 hours of FBS (27.3% vs 0%; P = .02) and the risk of prematurity (100.0% vs 13.3%; P < .001) were higher in fetuses with severe thrombocytopenia. Fetal thrombocytopenia was more common during the second trimester but, in some cases, persisted into the third trimester. Intrauterine transfusion (IUT) of red blood cells resulted in a further mean decrease of 40.1% ± 31.0% in fetal platelet concentration.

CONCLUSION

Severe fetal thrombocytopenia is relatively common after fetal hParvo-B19 infection, can be further worsened by IUT, and may be associated with an increased risk of procedure-related fetal loss after either FBS or IUT.

Human platelet antigen (HPA)-1a peptides do not reliably suppress anti-HPA-1a responses using a humanized severe combined immunodeficiency (SCID) mouse model

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) occurs most frequently when human platelet antigen (HPA)-1a-positive fetal platelets are destroyed by maternal HPA-1a immunoglobulin (Ig)G antibodies. Pregnancies at risk are treated by administration of high-dose intravenous Ig (IVIG) to women, but this is expensive and often not well tolerated. Peptide immunotherapy may be effective for ameliorating some allergic and autoimmune diseases. The HPA-1a/1b polymorphism is Leu/Pro33 on β3 integrin (CD61), and the anti-HPA-1a response is restricted to HPA-1b1b and HLA-DRB3*0101-positive pregnant women with an HPA-1a-positive fetus. We investigated whether or not HPA-1a antigen-specific peptides that formed the T cell epitope could reduce IgG anti-HPA-1a responses, using a mouse model we had developed previously. Peripheral blood mononuclear cells (PBMC) in blood donations from HPA-1a-immunized women were injected intraperitoneally (i.p.) into severe combined immunodeficient (SCID) mice with peptides and HPA-1a-positive platelets. Human anti-HPA-1a in murine plasma was quantitated at intervals up to 15 weeks. HPA-1a-specific T cells in PBMC were identified by proliferation assays. Using PBMC of three donors who had little T cell reactivity to HPA-1a peptides in vitro, stimulation of anti-HPA-1a responses by these peptides occurred in vivo. However, with a second donation from one of these women which, uniquely, had high HPA-1a-specific T cell proliferation in vitro, marked suppression of the anti-HPA-1a response by HPA-1a peptides occurred in vivo. HPA-1a peptide immunotherapy in this model depended upon reactivation of HPA-1a T cell responses in the donor. For FNAIT, we suggest that administration of antigen-specific peptides to pregnant women might cause either enhancement or reduction of pathogenic antibodies.

Diagnosis and management of neonatal alloimmune thrombocytopenia in pregnancy

Neonatal alloimmune thrombocytopenia (NAIT) is the most common cause of severe thrombocytopenia in the healthy newborn, occurring in 1 in 1000 live births. NAIT is analogous to rhesus alloimmunization in pathophysiology; however, it often presents unexpectedly in first pregnancies. Presentation of NAIT varies from mild thrombocytopenia to life-threatening intracranial hemorrhage. It has been observed to be more severe in subsequent affected pregnancies. It is important that the diagnosis of NAIT be considered in the work-up of all cases of neonatal thrombocytopenia to determine the risk to future pregnancies and corresponding management plans. This article discusses the pathogenesis and incidence of NAIT and the antenatal and postnatal management of this condition.

Recombinant HPA-1a antibody therapy for treatment of fetomaternal alloimmune thrombocytopenia: proof of principle in human volunteers

Fetomaternal alloimmune thrombocytopenia, caused by the maternal generation of antibodies against fetal human platelet antigen-1a (HPA-1a), can result in intracranial hemorrhage and intrauterine death. We have developed a therapeutic human recombinant high-affinity HPA-1a antibody (B2G1Δnab) that competes for binding to the HPA-1a epitope but carries a modified constant region that does not bind to Fcγ receptors. In vitro studies with a range of clinical anti-HPA-1a sera have shown that B2G1Δnab blocks monocyte chemiluminescence by >75%. In this first-in-man study, we demonstrate that HPA-1a1b autologous platelets (matching fetal phenotype) sensitized with B2G1Δnab have the same intravascular survival as unsensitized platelets (190 hours), while platelets sensitized with a destructive immunoglobulin G1 version of the antibody (B2G1) are cleared from the circulation in 2 hours. Mimicking the situation in fetuses receiving B2G1Δnab as therapy, we show that platelets sensitized with a combination of B2G1 (representing destructive HPA-1a antibody) and B2G1Δnab survive 3 times as long in circulation compared with platelets sensitized with B2G1 alone. This confirms the therapeutic potential of B2G1Δnab. The efficient clearance of platelets sensitized with B2G1 also opens up the opportunity to carry out studies of prophylaxis to prevent alloimmunization in HPA-1a-negative mothers.

A review of the contemporary management of fetal and neonatal alloimmune thrombocytopenia in an Australian tertiary obstetric hospital

BACKGROUND

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is the most common cause of severe perinatal thrombocytopenia, arising from the transplacental passage of maternal antibodies directed at paternally inherited antigens on fetal platelets.

AIM

To review the occurrence, management and perinatal outcomes of pregnancies complicated by FNAIT from a single tertiary obstetric hospital in Western Australia.

MATERIALS AND METHODS

The study was conducted as a retrospective review of cases with prenatally recognised FNAIT between 2001 and 2011, with the treatment modalities and outcomes analysed.

RESULTS

Over the 10-year period, 20 cases of clinically significant FNAIT in 13 women were managed at our centre. Three cases were complicated by antenatal intracranial haemorrhage (15%), and in all 3, this was the presenting feature leading to diagnosis. In 17/20 (85%) cases, anti-HPA 1a was the responsible antibody, with the remainder being anti-HPA 5b. In 16/17 cases with pre-pregnancy recognition, intravenous gammaglobulin (IVGG) was administered antenatally (gestation at commencement ranging from 13 to 26 weeks) with adjuvant prednisolone in three cases. Postnatal treatment (IVGG or platelet transfusion) was provided in 4/16 cases. There was no intracranial haemorrhage or demise in any case receiving prenatal therapy.

CONCLUSIONS

FNAIT is a rare and serious condition. In our small single-centre study, there was variability in the therapeutic strategies, although IVGG was central to all prenatally managed pregnancies. None of the treated pregnancies was complicated by intracranial haemorrhage or fetal death. There is a need for ongoing refinement of FNAIT management protocols, both in the prenatal and in the postnatal period.

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.

Repeated intrauterine IgG infusions in foetal alloimmune thrombocytopenia do not increase foetal platelet counts

BACKGROUND AND OBJECTIVES

Foetal alloimmune thrombocytopenia (FNAIT) is often treated transplacentally with maternally administered i.v. immunoglobulins, but not all foetuses show a consistent platelet increase during such treatment.

MATERIALS AND METHODS

We retrospectively analysed data from a cohort of ten foetuses with FNAIT treated by direct foetal immunoglobulin infusion. Foetal treatment was begun between 17 and 25 weeks and continued until 36 weeks with weekly cordocenteses and foetal immunoglobulin infusions.

RESULTS

While foetal IgG levels increased steadily during weekly IgG infusions, foetal platelet counts remained unchanged.

CONCLUSION

Our retrospective study presents a unique analysis of a historical cohort, contributing to the ongoing debate about the treatment of choice for foetal alloimmune thrombocytopenia.

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 4×10(9)/L and 130×10(9)/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.

Fetomaternal alloimmune thrombocytopenia: The questions that still remain

Fetomaternal alloimmune thrombocytopenia (FMAIT) occurs when maternal antibodies are formed to fetal platelet antigens, leading to thrombocytopenia and hemorrhagic complications. The diagnosis is frequently made only after a major hemorrhagic event has occurred during a pregnancy. Identifying patients at risk remains difficult, and the optimal treatment regimen remains to be determined.

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.

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.

Severe fetal thrombocytopenia in Rhesus D alloimmunized pregnancies

OBJECTIVE

The objective of the study was to evaluate the incidence of fetal thrombocytopenia and association with hydrops in Rhesus D alloimmunization.

STUDY DESIGN

The study was a retrospective chart review of 914 intrauterine transfusions in 314 pregnancies performed between 1988 and 2005 in a single institution. The incidence of thrombocytopenia and severity of hydrops at cordocentesis were assessed and correlated with perinatal mortality.

RESULTS

Thrombocytopenia (less than 150 x 10(9)/L) was found in 241 of 914 (26%) and severe thrombocytopenia (less than 50 x 10(9)/L) in 25 of 914 (3%) cordocentesis. Twenty-three percent of severely hydropic fetuses had severe thrombocytopenia, compared with 3% and 1% of mildly hydropic and nonhydropic fetuses, respectively. Thrombocytopenia was an independent risk factor for perinatal mortality. Mortality in fetuses that were severely thrombocytopenic and severely hydropic was 67%.

CONCLUSION

Thrombocytopenia is common in hydropic anemic fetuses. Severe thrombocytopenia is associated with a poor prognosis, irrespective of the presence of hydrops. The option of platelet transfusion in severely hydropic anemic fetuses needs further study.

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.

Neonatal thrombocytopenia

Thrombocytopenia (platelets <150 x 10(9)/L) is one of the most common haematological problems in neonates, particularly those who are preterm and sick. In those preterm neonates with early thrombocytopenia who present within 72 h of birth, the most common cause is reduced platelet production secondary to intrauterine growth restriction and/or maternal hypertension. By contrast, the most common causes of thrombocytopenia arising after the first 72 h of life, both in preterm and term infants, are sepsis and necrotizing enterocolitis. The most important cause of severe thrombocytopenia (platelets <50 x 10(9)/L) is neonatal alloimmune thrombocytopenia (NAIT), as diagnosis can be delayed and death or long-term disability due to intracranial haemorrhage may occur. Platelet transfusion is the mainstay of treatment for severe thrombocytopenia. However, the correlation between thrombocytopenia and bleeding is unclear and no studies have yet shown clinical benefit for platelet transfusion in neonates. Studies to identify optimal platelet transfusion practice for neonatal thrombocytopenia are urgently required.

Fetal thrombocytopenia

Fetal thrombocytopenia is most often caused by maternal alloantibodies against fetal platelets crossing the placenta and resulting in platelet destruction. This condition, known as fetal and neonatal alloimmune thrombocytopenia, is usually detected after the birth of a symptomatic child who shows signs of bleeding in the skin or in the brain. In the most severe cases, intracranial hemorrhage leads to severe handicap or death. The challenge for the clinician is to provide preventive treatment in the next pregnancy. The current cornerstone of this treatment is maternal intravenous administration of immunoglobulins during the second half of pregnancy.

Thrombocytopenia in the neonate

Thrombocytopenia is one of the commonest haematological problems in neonates, affecting at least 25% of all admissions to neonatal intensive care units (NICUs) [Murray NA, Howarth LJ, McCloy MP et al. Platelet transfusion in the management of severe thrombocytopenia in neonatal intensive care unit patients. Transfus Med 2002;12:35-41; Garcia MG, Duenas E, Sola MC et al. Epidemiologic and outcome studies of patients who received platelet transfusions in the neonatal intensive care unit. J Perinatol 2001;21:415-20; Del Vecchio A, Sola MC, Theriaque DW et al. Platelet transfusions in the neonatal intensive care unit: factors predicting which patients will require multiple transfusions. Transfusion 2001;41:803-8]. Although a long list of disorders associated with neonatal thrombocytopenia can be found in many textbooks, newer classifications based on the timing of onset of thrombocytopenia (early vs. late) are more useful for planning diagnostic investigations and day-to-day management. The mainstay of treatment of neonatal thrombocytopenia remains platelet transfusion although it is important to note that no studies have yet shown clinical benefit of platelet transfusion in this setting. Indeed some reports even suggest that there may be significant adverse effects of platelet transfusion in neonates, including increased mortality, and that the effects of transfusion may differ in different groups of neonates with similar degrees of thrombocytopenia [Bonifacio L, Petrova A, Nanjundaswamy S, Mehta R. Thrombocytopenia related neonatal outcome in preterms. Indian J Pediatr 2007;74:269-74; Kenton AB, Hegemier S, Smith EO et al. Platelet transfusions in infants with necrotizing enterocolitis do not lower mortality but may increase morbidity. J Perinatol 2005;25:173-7]. There is also considerable variation in transfusion practice between different countries and between different neonatal units. Here we review recent progress in understanding the prevalence, causes and pathogenesis of thrombocytopenia in the newborn, the clinical consequences of thrombocytopenia and developments in neonatal platelet transfusion.

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.

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.

Prospective epidemiologic study of the outcome and cost-effectiveness of antenatal screening to detect neonatal alloimmune thrombocytopenia due to anti-HPA-1a

BACKGROUND

To assess the value of antenatal screening to detect neonatal alloimmune thrombocytopenia (NAIT) due to anti-HPA-1a, a prospective study was carried out to quantify the potential clinical benefits and determine whether screening would be cost-effective.

STUDY DESIGN AND METHODS

An observational prospective controlled study was carried out on 26,506 pregnant women over 2 years. HPA-1a phenotyping was performed in the first trimester and women confirmed HPA-1a-negative were tested for anti-HPA-1a during pregnancy, at delivery, and 10 to 14 days after birth. Babies of HPA-1a-negative women were tested at delivery for thrombocytopenia and examined for signs of bleeding. Economic evaluation was undertaken on the basis of the data collected during the study.

RESULTS

Twenty-five of 318 women (7.9%) had anti-HPA-1a detected for the first time. Eight women (43 per 100,000) gave birth to babies with NAIT, and 5 (27 per 100,000) had severe thrombocytopenia. Three babies had mild signs of bleeding, and no cases of intracranial hemorrhage (ICH) or fetal loss were detected. It is estimated that it would cost 60,596 pounds (98,771 US dollars) to detect a case of severe NAIT, where anti-HPA-1a has been identified for the first time, and 1,151,323 pounds (1,876,656 US dollars) to prevent a case of ICH, assuming that detection allowed successful intervention.

CONCLUSIONS

Our data suggest that severe HPA-1a NAIT is underdiagnosed in the absence of routine antenatal screening. Serious bleeding complications and ICH, however, occur less frequently in first cases of NAIT than suspected from the literature, and the costs of screening and possible intervention must be balanced against the procedural risks.

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%.

Fatal fetal hemorrhage and placental pathology. Report of three cases and a new setting

We report three cases of late third trimester fetal death in utero consequent to fetal exsanguination from the chorionic vasculature. In general, fetal hemorrhage is unusual, exsanguination is rare and the location and basis of the hemorrhage varies widely. Intragestational and intrapartum hemorrhage is far more often of maternal rather than fetal origin. Even when severe, the former is almost always manageable whilst the latter may be clinically obscure, intractable, catastrophic and fatal. In this presentation, we review and characterize fetal hemorrhage by anatomical location and on the basis of its underlying origins. In our first two cases, the chorionic vascular failure is understood on the basis of mechanical factors, such as tearing by the presenting part or an amniotomy hook. Our third case demonstrates the first reported instance in which a severe chorionic vasculopathy has damaged a placental surface vessel sufficiently to permit spontaneous rupture and fetal exsanguination.

The evidence base for fetal medicine

This chapter looks at the evidence base for the practice of fetal medicine and surgery. There is very little good-quality research and much activity is based on case reports and series. However, the philosophy of evidence-based practice is now accepted and new randomized trials are being published in the literature (e.g. fetal endoscopic tracheal occlusion for congenital diaphragmatic hernia and laser treatment of the twin-to-twin transfusion syndrome). Many well established techniques would not be suitable for randomized trials but, as new techniques related to established practice are introduced (e.g. middle cerebral artery Doppler assessment), well-designed trials are essential to ensure they are safe, clinically useful and at least as good as standard practice. In this unique area of medicine, where ethical and emotional issues interplay with clinical practice, it is important not to introduce exciting techniques without solid evidence that they are beneficial both in the short and the long term.

Antenatal interventions for fetomaternal alloimmune thrombocytopenia

BACKGROUND

Fetomaternal alloimmune thrombocytopenia occurs when the mother produces antibodies against a platelet alloantigen that the fetus has inherited from the father. A consequence of this can be a reduced number of platelets (thrombocytopenia) in the fetus, which can result in bleeding whilst in the womb or shortly after birth. In severe cases this bleeding may lead to long-lasting disability or death. Antenatal management of fetomaternal alloimmune thrombocytopenia centres on preventing severe thrombocytopenia in the fetus. Available management options include administration of intravenous immunoglobulins or corticosteroids to the mother or intrauterine transfusion of antigen compatible platelets to the fetus. All options are costly and need to be assessed in terms of potential risk and benefit to both the mother and an individual fetus.

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 trials register (February 2004), EMBASE (1980 to February 2004) and bibliographies of relevant publications and review articles.

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed eligibility, trial quality and extracted data.

MAIN RESULTS

One study met the inclusion criteria (54 pregnant women). This trial compared intravenous immunoglobulins plus corticosteroid (dexamethasone) with intravenous immunoglobulins alone. No significant differences were reported between the treatment and control groups, in any outcome measured: mean platelet count at birth (weighted mean difference (WMD) 14.10 x 10 9/l, 95% confidence interval (CI) -30.26 to 58.46), mean gestational age at birth (WMD -0.50 weeks, 95% CI -2.69 to 1.69), mean rise in platelet count from first to second fetal blood screen (WMD -3.50 x 10 9/l, 95% CI -24.62 to 17.62) and mean rise in platelet count from birth to first fetal blood screen (WMD 24.40 x 10 9/l (95% CI -14.17 to 62.97)). This trial had adequate methodological quality; however the method used to calculate sample size was inappropriate: therefore the power calculation was not sufficient to determine any significance in differences between the treatment groups.

AUTHORS' CONCLUSIONS

There are insufficient data from randomised controlled trials to determine the optimal antenatal management of fetomaternal alloimmune thrombocytopenia. Future trials should consider the dose of intravenous immunoglobulins, the timing of initial treatment, monitoring of response to treatment by fetal blood sampling, laboratory measures to define pregnancies with a high risk of intercranial haemorrhage, management of non-responders and long-term follow up of children.