Fetal alloimmune thrombocytopenia and maternal intravenous immunoglobulin infusion

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.

Neonatal Immune Incompatibilities between Newborn and Mother

Background: Incompatibilities between the mother and unborn baby can cause complications that must be identified early to initiate the appropriate treatment. For example, neonatal alloimmune thrombocytopenia (NAIT), neonatal alloimmune neutropenia (NAIN), and morbus hemolyticus neonatorum affect children worldwide. Aim: This literature review aims to depict the similarities and differences between these three disorders from a clinical and mechanistic point of view. Material and Methods: The current literature review entailed conducting a systematic search to locate articles on the three conditions. Different electronic databases, including PsycINFO, PubMed, Web of Science, and CINAHL, were searched using the search terms "neonatal alloimmune thrombocytopenia", "neonatal alloimmune neutropenia", "morbus hemolyticus neonatorum", "NAIT", "FNAIT", "fetal", "NAIN", and "hemolytic disease of the newborn". Results: This review shows that these three diseases are caused by incompatibilities between the maternal and fetal immune systems. Furthermore, these conditions can lead to severe complications that hinder fetal development and cause death if not well managed. Discussion: The current literature review shows that NAIT, NAIN, and morbus hemolyticus neonatorum are rare conditions that occur when the mother produces antibodies against the fetal immune system. Thus, there is a need for the early detection of these conditions to initiate appropriate treatment before the child experiences adverse effects. Conclusion: The development of NAIT, NAIN, and morbus hemolyticus neonatorum is linked to the production of antibodies against the fetal immune system and fetal antigens. Further studies are required to determine potential interventions to reduce the risk of developing these three conditions.

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.

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.

A rare manifestation of neonatal alloimmune thrombocytopaenia

Neonatal alloimmune thrombocytopaenia (NAIT) results from a fetomaternal incompatibility with maternal sensitisation against a fetal human platelet antigen (HPA) and antibodies transfer to the fetal circulation, leading to platelet destruction. The clinical presentation is variable and isolated intraocular haemorrhage is rare. We present the case of a male newborn, with intrauterine growth restriction, born at 29 weeks due to pre-eclampsia. He presented proptosis of the left eye, hyphaema and elevated intraocular pressure, with no other signs of haemorrhage. Severe thrombocytopaenia was found (27×10(9)/L). Perinatal infection and maternal thrombocytopaenia were excluded. Positive anti-HPA-1a and antihuman leucocyte antigen class I alloantibodies were found in the mother. Platelet crossmatch between the father's platelets and mother's plasma was positive. Platelet transfusions and intravenous immunoglobulin were given with favourable response. This case highlights an unusual presentation of NAIT, which should be suspected in the presence of severe thrombocytopaenia in the first 24-72 h of life.

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.

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.

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.