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

Generation of human antibodies targeting human platelet antigen (HPA)-1a

BACKGROUND

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a condition during pregnancy, which can lead to thrombocytopenia and a bleeding tendency with intracranial hemorrhage (ICH) being the most concerning complication in the fetus or neonate. An incompatibility between human platelet antigen (HPA)-1a accounts for the majority of FNAIT cases. Binding of HPA-1a-specific alloantibodies to their target on fetal platelets and endothelial cells can induce apoptosis of megakaryocytes, disrupt platelet function, and impair angiogenesis. Currently, there is no screening program to identify pregnancies at risk for severe disease. A better understanding of HPA-1a-specific antibody heterogeneity in FNAIT could aid in identifying pathogenic antibody properties linked to severe disease.

STUDY DESIGN AND METHODS

This study aimed to isolate HPA-1a-specific B-cells from an HPA-1a-alloimmunized pregnant woman. Using fluorescently labeled HPA-1a-positive platelets, single B-cells were sorted and cultured for 10 days to stimulate antibody production. Subsequently, supernatants were tested for the presence of antibodies by enzyme-linked immunosorbent assay and their reactivity towards HPA-1a-positive platelets. Amplification and sequencing of variable regions allowed the generation of monoclonal antibodies using a HEK-Freestyle-based expression system.

RESULTS

Three platelet-specific B-cells were obtained and cloned of which two were specific for HPA-1a, named D- and M-204, while the third was specific for HLA class I, which was named L-204.

DISCUSSION

This study outlined an effective method for the isolation of HPA-1a-specific B-cells and the generation of monoclonal antibodies. Further characterization of these antibodies holds promise for better understanding the pathogenic nature of alloantibodies in FNAIT.

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.

Natural history of human platelet antigen 1a-alloimmunised pregnancies: a prospective observational cohort study

BACKGROUND

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare disease that untreated can lead to intracranial haemorrhage or death. The natural history of FNAIT is still unclear; therefore, the benefits of screening cannot be estimated and no routine screening is yet in place. We aimed to assess the incidence of clinically detectable FNAIT among pregnancies in human platelet antigen-1a (HPA-1a)-immunised women.

METHODS

We did a prospective observational cohort study of pregnant women negative for rhesus D (RhD) and rhesus c (Rhc) antigens, without age limits, who underwent routine antenatal screening for red cell antibodies at 27 weeks' gestation and were typed for HPA-1a between March 1, 2017, and May 1, 2020. HPA-1a-negative women were tested for HPA alloantibodies. Health-care professionals were masked to all test results. The main outcome was the proportion of neonates with severe, clinically detectable FNAIT, defined as having an intracranial bleed, organ bleed, or bleeding-related death observed during pregnancy or within the first week of life. Cases of clinically detectable FNAIT not categorised as severe were categorised as mild. This study is registered with ClinicalTrials.gov (NCT04067375).

FINDINGS

Of 153 106 women typed for HPA-1a, 3722 (2·4%) were negative for HPA-1a. 913 HPA-1a-negative women gave informed consent, underwent HPA-1a antibody screening, and were included in the study. Anti-HPA-1a antibodies were detected in 85 HPA-1a-negative participants, among whom three with HPA-1a-negative fetuses and one with a previous child with FNAIT were excluded. As controls, 820 HPA-1a-negative, non-immunised pregnancies and 2704 randomly selected pregnancies of women negative for RhD and Rhc who were typed HPA-1a positive were included. Of 81 fetuses included, one (1·2%) was diagnosed with severe HPA-1a-mediated intracranial haemorrhage and three (3·7%) had mild FNAIT. Gravidity and parity did not seem to be risk factors for HPA-1a immunisation. 73 (90·1%) of 81 HPA-1a-immunised women were positive for HLA-DRB3*01:01.

INTERPRETATION

Our data suggest that, without intervention, the incidence of major clinically detectable bleeding in FNAIT is estimated as 11 (95% CI 0-32) per 10 000 HPA-1a-negative pregnancies. These findings imply that severe bleeding is a rare event that potentially could be prevented by a screening programme.

FUNDING

Landsteiner Foundation for Blood Transfusion Research and Sanquin.

Navigating the Storm: Managing Fetal and Neonatal Alloimmune Thrombocytopenia (FNAIT) in a High-Risk Pregnancy

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare, life-threatening condition causing significant thrombocytopenia and bleeding with the risk of developing intracerebral hemorrhage (ICH). It results from maternal immunizations against fetal platelet antigens. Here, we report a case of a pregnant patient at 30 weeks gestation who presented to the hospital with a low platelet count of 90 th/mm3 and was found to have anti-human platelet antigen (HPA) 1a, 2b antibodies. She was treated with a weekly infusion of IV immunoglobulins. However, her condition was complicated by the development of hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome, which was treated promptly with a platelet transfusion and intravenous magnesium. Even though the child had severe thrombocytopenia and its associated complications, there were no signs of post-delivery thrombocytopenia or any other adverse effects. This case report highlights the importance of the antenatal management of the FNAIT to prevent severe fetal complications, such as ICH.

Cellular surface plasmon resonance-based detection of anti-HPA-1a antibody glycosylation in fetal and neonatal alloimmune thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) can occur due to maternal IgG antibodies targeting platelet antigens, causing life-threatening bleeding in the neonate. However, the disease manifests itself in only a fraction of pregnancies, most commonly with anti-HPA-1a antibodies. We found that in particular, the core fucosylation in the IgG-Fc tail is highly variable in anti-HPA-1a IgG, which strongly influences the binding to leukocyte IgG-Fc receptors IIIa/b (FcγRIIIa/b). Currently, gold-standard IgG-glycoanalytics rely on complicated methods (e.g., mass spectrometry (MS)) that are not suited for diagnostic purposes. Our aim was to provide a simplified method to quantify the biological activity of IgG antibodies targeting cells. We developed a cellular surface plasmon resonance imaging (cSPRi) technique based on FcγRIII-binding to IgG-opsonized cells and compared the results with MS. The strength of platelet binding to FcγR was monitored under flow using both WT FcγRIIIa (sensitive to Fc glycosylation status) and mutant FcγRIIIa-N162A (insensitive to Fc glycosylation status). The quality of the anti-HPA-1a glycosylation was monitored as the ratio of binding signals from the WT versus FcγRIIIa-N162A, using glycoengineered recombinant anti-platelet HPA-1a as a standard. The method was validated with 143 plasma samples with anti-HPA-1a antibodies analyzed by MS with known clinical outcomes and tested for validation of the method. The ratio of patient signal from the WT versus FcγRIIIa-N162A correlated with the fucosylation of the HPA-1a antibodies measured by MS (r=-0.52). Significantly, FNAIT disease severity based on Buchanan bleeding score was similarly discriminated against by MS and cSPRi. In conclusion, the use of IgG receptors, in this case, FcγRIIIa, on SPR chips can yield quantitative and qualitative information on platelet-bound anti-HPA-1a antibodies. Using opsonized cells in this manner circumvents the need for purification of specific antibodies and laborious MS analysis to obtain qualitative antibody traits such as IgG fucosylation, for which no clinical test is currently available.

Pregnant Women at Low Risk of Having a Child with Fetal and Neonatal Alloimmune Thrombocytopenia Do Not Require Treatment with Intravenous Immunoglobulin

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare condition in which maternal alloantibodies to fetal platelets cause fetal thrombocytopenia that may lead to intracranial hemorrhage (ICH). Off-label intravenous immunoglobulin (IVIg) has for 30 years been the standard of care for pregnant women who previously have had a child with FNAIT. The efficacy of this treatment has never been tested in a placebo-controlled clinical trial. Although IVIg treatment may improve the neonatal outcome in women who previously have had a child with FNAIT-associated ICH, the question is whether IVIg is necessary for all immunized pregnant women at risk of having a child with FNAIT. The results from some recent publications suggest that antenatal IVIg treatment is not necessary for women who are (1) HPA-1a-immunized and HLA-DRB3*01:01-negative, (2) HPA-1a-immunized with a previous child with FNAIT but without ICH or (3) HPA-5b-immunized. If IVIg is not used for these categories of pregnant women, the amount of IVIg used in pregnant women with platelet antibodies would be reduced to less than ¼ of today's use. This is important because IVIg is a scarce resource, and the collection of plasma for the treatment of one pregnant woman is not only extremely expensive but also requires tremendous donor efforts.

Fetal and neonatal alloimmune thrombocytopenia: A rare case report of prenatal treatment

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare but serious condition. The first-line antenatal management of FNAIT consists of weekly IVIG with or without corticosteroids, ideally starting before 16 weeks of gestation.

Children Newly Diagnosed with Fetal and Neonatal Alloimmune Thrombocytopenia: Neurodevelopmental Outcome at School Age

OBJECTIVE

To evaluate the neurodevelopmental outcome at school age in children newly diagnosed with fetal and neonatal alloimmune thrombocytopenia (FNAIT).

STUDY DESIGN

This observational cohort study included children diagnosed with FNAIT between 2002 and 2014. Children were invited for cognitive and neurological testing. Behavioral questionnaires and school performance results were obtained. A composite outcome of neurodevelopmental impairment (NDI) was used, defined, and subdivided into mild-to-moderate and severe NDI. Primary outcome was severe NDI, defined as IQ <70, cerebral palsy with Gross Motor Functioning Classification System level ≥ III, or severe visual/hearing impairment. Mild-to-moderate NDI was defined as IQ 70-85, minor neurological dysfunction or cerebral palsy with Gross Motor Functioning Classification System level ≤ II, or mild visual/hearing impairment.

RESULTS

In total, 44 children were included at a median age of 12 years (range: 6-17 years). Neuroimaging at diagnosis was available in 82% (36/44) of children. High-grade intracranial hemorrhage (ICH) was detected in 14% (5/36). Severe NDI was detected in 7% (3/44); two children had high-grade ICH, and one had low-grade ICH and perinatal asphyxia. Mild-to-moderate NDI was detected in 25% (11/44); one child had high-grade ICH, and eight children were without ICH, yet for two children, neuroimaging was not performed. Adverse outcome (perinatal death or NDI) was 39% (19/49). Four children (9%) attended special needs education, three of whom had severe NDI and one had mild-to-moderate NDI. Total behavioral problems within the clinical range were reported in 12%, which is comparable with 10% in the general Dutch population.

CONCLUSION

Children who are newly diagnosed with FNAIT are at increased risk for long-term neurodevelopmental problems, even those without ICH.

TRIAL REGISTRATION

The study was registered at ClinicalTrials.gov (Identifier: NCT04529382).

Bernard-Soulier Syndrome from the Perspective of the Obstetrician: A Case Report with a Review of the Literature

OBJECTIVE

Bernard-Soulier syndrome (BSS) is one of the rare inherited platelet disorders that is characterized by macrothrombocytopenia and adhesion abnormality due to the absence or malfunctioning of the membrane GPIb-IX-V complex. There is no high-quality evidence on obstetric management of BSS owing to its rarity. Here we report an uncomplicated delivery of an adolescent with BSS and review the literature on the topic of BSS and pregnancy.

METHODS

PUBMED, EMBASE, COCHRANE, and Google Scholar databases were searched up to April 2022 without language and year restriction using the terms "Bernard Soulier" and "Pregnancy". The primary objectives were to evaluate maternal and fetal outcomes. The secondary objectives were to analyze pregnancy complications, gestational age at delivery, mode of delivery, administered prophylaxis, treatment approaches, duration of postpartum hospitalization, and the postpartum requirement of blood and blood product.

RESULTS

The patient was a 19-year-old and 39-week pregnant woman who was diagnosed with BSS at the age of 10 by flow cytometry and genetic analysis. Single donor platelet transfusions and oral tranexamic acid were administered as prophylaxis at the peripartum period. She was delivered by cesarean section due to failure of labor. The postpartum period was uneventful for both mother and neonate. In the literature review, postpartum hemorrhage (PPH) was found in 52.9% (27/51) of deliveries. Late PPH occurred more frequently than early PPH (35.3 and 31.4%, respectively). 49% (25/51) of pregnancies had severe thrombocytopenia, and antepartum hemorrhage was observed in 11.8% (6/51) of those. The platelet count was in close relation to antenatal complications. 64.7% (33/51) of the patients were delivered via cesarean section. PPH and late PPH were found to be more common in those who delivered vaginally compared to those who delivered by caesarean section. It was observed that PPH was less common in women who were given prophylaxis in the peripartum period.

CONCLUSION

BSS is an inherited macro-thrombocytopathy that may cause adverse maternal and neonatal outcomes. The optimal mode and timing of delivery remain unclear. A multidisciplinary approach with prophylaxis at the peripartum period should be applied.

Fetal and neonatal alloimmune thrombocytopenia: Current pathophysiological insights and perspectives for future diagnostics and treatment

FNAIT is a pregnancy-associated condition caused by maternal alloantibodies against paternally-inherited platelet antigens, most frequently HPA-1a on integrin β3. The clinical effects range from no symptoms to fatal intracranial hemorrhage, but underlying pathophysiological determinants are poorly understood. Accumulating evidence suggests that differential antibody-Fc-glycosylation, activation of complement/effector cells, and integrin function-blocking effects contribute to clinical outcome. Furthermore, some antibodies preferentially bind platelet integrin αIIbβ3, but others bind αvβ3 on endothelial cells and trophoblasts. Defects in endothelial cells and angiogenesis may therefore contribute to severe anti-HPA-1a associated FNAIT. Moreover, anti-HPA-1a antibodies may cause placental damage, leading to intrauterine growth restriction. We discuss current insights into diversity and actions of HPA-1a antibodies, gathered from clinical studies, in vitro studies, and mouse models. Assessment of all factors determining severity and progression of anti-HPA-1a-associated FNAIT may importantly improve risk stratification and potentially reveal novel treatment strategies, both for FNAIT and other immunohematological disorders.

Clinical and laboratory predictors of fetal and neonatal alloimmune thrombocytopenia

BACKGROUND

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is the most common cause of intracranial hemorrhage (ICH) in thrombocytopenic term infants. We investigated clinical and laboratory predictors of severe FNAIT in a tertiary care referral center.

STUDY DESIGN AND METHODS

Retrospective cohort study over a 30-year period. We defined FNAIT as recurrence of neonatal thrombocytopenia in a subsequent pregnancy; and severe outcomes as any of: (1) a birth platelet count below 20 × 10⁹ /L; (2) ICH or (3) fetal death. We used a generalized estimating equations analysis and classification tree analysis to identify risk factors for severe FNAIT in a subsequent pregnancy.

RESULTS

During index pregnancies (n = 135 in 131 mothers), 71 infants (52.6%) had severe outcomes including a platelet count <20 × 10⁹ /L (n = 45), fetal or neonatal ICH (n = 32), or fetal death (n = 4). During subsequent pregnancies (n = 72), 15 infants (20.8%) had severe outcomes including birth platelets <20 × 10⁹ /L (n = 10), ICH (n = 2), or death (n = 3). Forty-two women (58.3%) received antenatal intravenous immune globulin (IVIG) during subsequent pregnancies. Eight mothers (n = 9 infants) had severe FNAIT outcomes despite receiving antenatal IVIG. Maternal antibodies to human platelet antigens (HPA) was the only independent predictor of severe FNAIT in a subsequent pregnancy (OR = 25.3, p = .004). Nevertheless, one of 43 infants from antibody-negative mothers had a severe outcome.

CONCLUSIONS

The presence of anti-HPA is highly indicative of the diagnosis of severe FNAIT; however, we observed one infant who had severe FNAIT recurrence, defined using strict clinical criteria, without a maternal antibody. Improved diagnostic and therapeutic strategies are needed to prevent severe FNAIT in high-risk mothers.

Targeting neonatal Fc receptor: potential clinical applications in pregnancy

The neonatal Fc receptor (FcRn) plays an important role in the transfer of the immunoglobulin G isotype (IgG) from the mother to the fetus. FcRn expressed on endothelial cells also binds to IgG and albumin, regulating the circulating half-lives of these proteins. Alloimmune and autoimmune IgG antibodies have been implicated in various perinatal immune-mediated diseases. FcRn-mediated placental transfer of pathogenic antibodies can result in cell and tissue injury in the fetus and neonate, with devastating outcomes. Thus, blockade of FcRn may be an effective treatment strategy in managing these conditions and could additionally reduce the concentration of pathogenic antibodies in the maternal circulation by preventing IgG recycling. In this review, we discuss the biology of FcRn, the rationale and considerations for development of FcRn-blocking agents, and their potential clinical applications in various perinatal immune-mediated diseases. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Immune-Mediated Neonatal Thrombocytopenia

Immune-mediated thrombocytopenia in neonates is caused by the transplacental passage of maternally derived antiplatelet antibodies. The 2 most common causes include neonatal alloimmune thrombocytopenia, which leads to significant thrombocytopenia and risk of intracranial hemorrhage, and autoimmune thrombocytopenia, which is generally less severe. No specific guidelines for prenatal management exist for either disease; however, intravenous immune globulin treatments and systemic steroids for women with at-risk pregnancies can be useful in both diseases. In this review, we discuss the current literature and management strategies for both pregnant women and newborns with immune-mediated thrombocytopenia.

Long-term neurodevelopmental outcome in children after antenatal intravenous immune globulin treatment in fetal and neonatal alloimmune thrombocytopenia

BACKGROUND

Children with fetal and neonatal alloimmune thrombocytopenia (FNAIT) face increased risk of intracranial hemorrhage (ICH) potentially leading to developmental impairment. To prevent ICH, pregnant women with alloantibodies against fetal platelets are often treated with intravenous immunoglobulin (IVIg). IVIg appears effective in vastly reducing the risk of fetal or neonatal bleeding complications. However, information on long-term neurodevelopment of these children is lacking.

OBJECTIVE

To evaluate long-term neurodevelopmental outcome in children with FNAIT who were treated with IVIg antenatally.

STUDY DESIGN

An observational cohort study was performed including children of mothers who were treated with IVIg during pregnancy because a previous child was diagnosed with FNAIT. Children, were invited for a follow-up assessment including standardized cognitive and neurologic tests. The parents were asked to complete a behavioral questionnaire and school performance reports. The primary outcome was severe neurodevelopmental impairment (NDI), defined as severe cognitive impairment (IQ < 70), cerebral palsy with Gross Motor Function Classification System (GMFCS) Level ≥ 3, bilateral blindness, and/or bilateral deafness (requiring amplification). The secondary outcome was mild to moderate NDI, defined as either mild to moderate cognitive impairment (IQ < 85), cerebral palsy with GMFCS Level ≤ 2, minor neurologic dysfunction, vision loss, and/or hearing loss.

RESULTS

Between 2003 and 2017, 51 children were liveborn after antenatal IVIg treatment. One family moved abroad and was therefore not eligible for inclusion. In total, 82% (41/50) of the eligible cases were included for neurodevelopmental assessment at a median age of 9 years and 8 months. Severe NDI was not detected. The incidence of mild to moderate NDI was 14% (6/41, 95% confidence interval: 6%-29%). The children's mean cognitive score, behavioral scores, and academic achievement were not different from the Dutch norm groups. Neuroimaging was performed in 90% (37/41) of cases. Severe ICH had been diagnosed in two cases (5%), one antenatally before the start of IVIg and the other case 1 day after birth. Both cases had a normal neurodevelopmental outcome.

CONCLUSION

The risk of NDI in children whose mothers were treated for FNAIT with antenatal IVIg is comparable to that in the general population.

Perinatal and long-term outcome of fetal intracranial hemorrhage: systematic review and meta-analysis

OBJECTIVE

Fetal intracranial hemorrhage (ICH) is associated with an increased risk of perinatal mortality and morbidity. Healthcare professionals often find it challenging to counsel parents due to its rarity and diverse presentation. The aim of this systematic review and meta-analysis was to investigate the perinatal outcome of fetuses with ICH.

METHODS

MEDLINE, EMBASE, ClinicalTrials.gov and The Cochrane Library databases were searched. Inclusion criteria were studies reporting the outcome of fetuses, newborns and infants diagnosed with ICH. The primary outcome was perinatal death (PND), defined as the sum of intrauterine (IUD) and neonatal death (NND). The secondary outcomes were stillbirth, NND, IUD, termination of pregnancy, need for surgery/shunting at birth, cerebral palsy (defined according to the European Cerebral Palsy Network and classified as diplegia, hemiplegia, quadriplegia, dyskinetic or mixed), neurodevelopmental delay and intact survival. All outcomes were explored in the included fetuses with ICH. A subgroup analysis according to the location of the hemorrhage (intra-axial and extra-axial) was also planned. Meta-analysis of proportions was used to combine data, and pooled proportions and their 95% CI were reported.

RESULTS

Sixteen studies (193 fetuses) were included in the meta-analysis. PND occurred in 14.6% (95% CI, 7.3-24.0%) of fetuses with ICH. Among liveborn cases, 27.6% (95% CI, 12.5-45.9%) required shunt placement or surgery after birth and 32.0% (95% CI, 22.2-42.6%) had cerebral palsy. Furthermore, 16.7% (95% CI, 8.4-27.2%) of cases had mild neurodevelopmental delay, while 31.1% (95% CI, 19.0-44.7%) experienced severe adverse neurodevelopmental outcome. Normal neurodevelopmental outcome was reported in 53.6% of fetuses. Subgroup analysis according to the location of ICH showed that PND occurred in 13.3% (95% CI, 5.7-23.4%) of fetuses with intra-axial bleeding and 26.7% (95% CI, 5.3-56.8%) of those with extra-axial bleeding. In fetuses with intra-axial hemorrhage, 25.2% (95% CI, 11.0-42.9%) required shunt placement or surgery after birth and 25.5% (95% CI, 15.3-37.2%) experienced cerebral palsy. In fetuses with intra-axial hemorrhage, mild and severe neurodevelopmental delay was observed in 14.9% (95% CI, 12.0-27.0%) and 32.8% (95% CI, 19.8-47.4%) of cases, respectively, while 53.2% (95% CI, 37.0-69.1%) experienced normal neurodevelopmental outcome. The incidence of mortality and postnatal neurodevelopmental outcome in fetuses with extra-axial hemorrhage could not be estimated reliably due to the small number of cases.

CONCLUSIONS

Fetuses with a prenatal diagnosis of ICH are at high risk of perinatal mortality and adverse neurodevelopmental outcome. Postnatal shunt placement or surgery was required in 28% of cases and cerebral palsy was diagnosed in approximately one-third of infants. Due to the rarity of ICH, multicenter prospective registries are warranted to collect high-quality data. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Antenatal intravenous immunoglobulins in pregnancies at risk of fetal and neonatal alloimmune thrombocytopenia: comparison of neonatal outcome in treated and nontreated pregnancies

BACKGROUND

Maternal alloantibodies to human platelet antigen-1a can cause severe intracranial hemorrhage in a fetus or newborn. Although never evaluated in placebo-controlled clinical trials, most Western countries use off-label weekly administration of high-dosage intravenous immunoglobulin in all pregnant women with an obstetrical history of fetal and neonatal alloimmune thrombocytopenia. In Norway, antenatal intravenous immunoglobulin is only recommended in pregnancies wherein a previous child had intracranial hemorrhage (high-risk) and is generally not given in other human platelet antigen-1a alloimmunized pregnancies (low-risk).

OBJECTIVE

To compare the frequency of anti-human platelet antigen-1a-induced intracranial hemorrhage in pregnancies at risk treated with intravenous immunoglobulin vs pregnancies not receiving this treatment as a part of a different management program.

STUDY DESIGN

This was a retrospective comparative study where the neonatal outcomes of 71 untreated human platelet antigen-1a-alloimmunized pregnancies in Norway during a 20-year period was compared with 403 intravenous-immunoglobulin-treated pregnancies identified through a recent systematic review. We stratified analyses on the basis of whether the mothers belonged to high- or low-risk pregnancies. Therefore, only women who previously had a child with fetal and neonatal alloimmune thrombocytopenia were included.

RESULTS

Two neonates with brain bleeds were identified from 313 treated low-risk pregnancies (0.6%; 95% confidence interval, 0.2-2.3). There were no neonates born with intracranial hemorrhage of 64 nontreated, low-risk mothers (0.0%; 95% confidence interval, 0.0-5.7). Thus, no significant difference was observed in the neonatal outcome between immunoglobulin-treated and untreated low-risk pregnancies. Among high-risk mothers, 5 of 90 neonates from treated pregnancies were diagnosed with intracranial hemorrhage (5.6%; 95% confidence interval, 2.4-12.4) compared with 2 of 7 neonates from nontreated pregnancies (29%; 95% confidence interval, 8.2-64.1; P=.08).

CONCLUSION

The most reliable data hitherto for the evaluation of intravenous immunoglobulins treatment in low-risk pregnancies is shown herein. We did not find evidence that omitting antenatal intravenous immunoglobulin treatment in low-risk pregnancies increases the risk of neonatal intracranial hemorrhage.

Fetal neonatal alloimmune thrombocytopenia treatment with intravenous immunoglobulin: a challenge in pregnancy management and infection assessment ‒ case report

Objectives

Fetal and neonatal alloimmune thrombocytopenia is a rare condition associated with fetal and neonatal morbimortality. Prevention of recurrence includes intravenous immunoglobulin. One challenge in pregnancy surveillance remains the fact that maternal intravenous immunoglobulins therapy can result in false-positive infectious markers. The goal of this case report is to highlight the possible serological misdiagnosed infection associated with intravenous immunoglobulins therapy in pregnancy, and the difficulty of management in this time of a women’s life.

Case presentation

We report a case of a 38-year-old pregnant woman, with a previous affected child with fetal neonatal alloimmune thrombocytopenia. To prevent recurrence, intravenous immunoglobulin treatment was administered in early second trimester. In the second trimester routine analysis, a positive anti-treponemal test and a toxoplasmosis seroconversion occurred. Infection suspicion based on test positivity of some infectious agents, after passive acquired antibodies, can lead to anxiety and subsequent unnecessary treatment.

Conclusions

Clinicians and pathologists must be aware of the possible acquisition of these antibodies during treatment and be able to counsel patients receiving intravenous immunoglobulin. Managing possible infectious intercurrences in pregnancy remains a challenge.

Prediction of fetal blood group antigens from maternal plasma using Ion AmpliSeq HD technology

BACKGROUND

Fetal blood group (BG) and platelet (HPA) antigens may trigger maternal immunization, causing a fetal disease. Noninvasive prenatal diagnostics (NIPT) predicts fetal genotype, identifying pregnancies with no risk. All current techniques detect fetal antigen alleles with unspecific background and without estimation of fetal fraction, thus new protocols for detection of fetal BG/HPA alleles with ultrahigh sensitivity still need to be tested to improve NIPT.

AIM

To design NIPT of clinically important antigens using Ion AmpliSeq HD technology.

METHODS

Plasma DNA from 36 pregnant women (9-33 week of gestation, 24 immunized with anti-HPA-1a,-3b,-15a, -K, or -D+C+S), with known BG/HPA genotypes of their neonates/partners, was tested on Ion S5 System using the Ion AmpliSeq HD designer custom gene panel. NGS contained 25 rs-targets encoding relevant BG/HPA antigens and 10 markers.

RESULTS

Using the NGS protocol, 76 out of 85 differences in fetal/maternal BG/HPA genotypes were determined in concentration above 2% fetal paternally inherited allele chimerism. The level of unspecific reads for BG/HPA alleles was below 0.87%. In 24 immunized women NGS revealed feto-maternal incompatibility in 11 cases (from 2.44% to 7.41%) and excluded in 10 (<0.05%), three cases had inconclusive results (1.79%, 0.19%, 0.11%). The presence of fetal DNA was confirmed in each case by detecting markers with at least 2% chimerism.

CONCLUSION

The use of Ion AmpliSeq HD technology improves the prediction of feto-maternal incompatibility, increasing the sensitivity of BG/HPA NIPT and serving confirmation of the fetal DNA at the same workflow.

Successful prenatal therapy for anti-CD36-mediated severe FNAIT by deglycosylated antibodies in a novel murine model

Recent studies have shown that maternal anti-CD36 antibodies represent a frequent cause of fetal/neonatal alloimmune thrombocytopenia (FNAIT) in Asian and African populations. However, little is known about the pathomechanism and antenatal treatment of anti-CD36-mediated FNAIT. Here, we established a novel animal model to examine the clinical features of pups from immunized Cd36-/- female mice after breeding with wild-type male mice. Mild thrombocytopenia was observed, but high pup mortality was also documented (40.26%). Administration of intravenous immunoglobulin (IVIG) (1 g/kg) on days 7, 12, and 17 to immunized Cd36-/- mothers after breeding reduced fetal death (12.70%). However, delaying the IVIG administration series on days 10, 15, and 20 did not reduce fetal death (40.00%). In contrast, injection of deglycosylated anti-CD36 (deg-anti-CD36) polyclonal antibodies (5 mg/kg) on days 10, 15, and 20 significantly reduced fetal death (5.26%). Subsequently, monoclonal antibodies (mAbs) against mouse CD36 were developed, and one clone producing high-affinity anti-CD36 (termed 32-106) effectively inhibited maternal antibody binding and was therefore selected. Using the same approach of deg-anti-CD36, the administration of deg-32-106 significantly reduced fetal death (2.17%). Furthermore, immunized Cd36-/- mothers exhibited placental deficiency. Accordingly, maternal anti-CD36 antibodies inhibited angiogenesis of placenta endothelial cells, which could be restored by deg-32-106. In summary, maternal anti-CD36 antibodies caused a high frequency of fetal death in our animal model, associated with placental dysfunction. This deleterious effect could be diminished by the antenatal administration of IVIG and deg-mAb 32-106. Interestingly, treatment with deg-32-106 seems more beneficial considering the lower dose, later start of treatment, and therapy success.

Preclinical evaluation of immunotherapeutic regimens for fetal/neonatal alloimmune thrombocytopenia

Fetal/neonatal alloimmune thrombocytopenia (FNAIT) is a life-threatening bleeding disorder caused by maternal antibodies directed against paternally inherited antigens present on the surface of fetal platelets. The human platelet alloantigen HPA-1a (formerly known as the PlA1 alloantigen), is the most frequently implicated HPA for causing FNAIT in Whites. A single Leu33Pro amino acid polymorphism residing within the ∼50-amino-acid plexin-semaphorin-integrin domain near the N-terminus of the integrin β3 subunit (platelet membrane glycoprotein IIIa [GPIIIa]) is responsible for generating the HPA-1a and HPA-1b epitopes in human GPIIIa and serves as the central target for alloantibody-mediated platelet destruction. To simulate the etiology of human FNAIT, wild-type female mice were pre-immunized with platelets derived from transgenic mice engineered to express the human HPA-1a epitope on a murine GPIIIa backbone. These mice developed a strong alloimmune response specific for HPA-1a, and when bred with HPA-1a+ males, gave birth to severely thrombocytopenic pups that exhibited an accompanying bleeding phenotype. Administering either polyclonal intravenous immunoglobulin G or a human monoclonal blocking antibody specific for the HPA-1a epitope into pregnant female mice resulted in significant elevation of the neonatal platelet count, normalized hemostasis, and prevented bleeding. The establishment of an alloantigen-specific murine model that recapitulates many of the clinically important features of FNAIT should pave the way for the preclinical development and testing of novel therapeutic and prophylactic modalities to treat or prevent FNAIT in humans.

Improving Human Induced Pluripotent Stem Cell-Derived Megakaryocyte Differentiation and Platelet Production

Several protocols exist for generating megakaryocytes (MKs) and platelets from human induced pluripotent stem cells (hiPSCs) with limited efficiency. We observed previously that mesoderm induction improved endothelial and stromal differentiation. We, therefore, hypothesized that a protocol modification prior to hemogenic endothelial cell (HEC) differentiation will improve MK progenitor (MKP) production and increase platelet output. We further asked if basic media composition affects MK maturation. In an iterative process, we first compared two HEC induction protocols. We found significantly more HECs using the modified protocol including activin A and CHIR99021, resulting in significantly increased MKs. MKs released comparable platelet amounts irrespective of media conditions. In a final validation phase, we obtained five-fold more platelets per hiPSC with the modified protocol (235 ± 84) compared to standard conditions (51 ± 15; p < 0.0001). The regenerative potency of hiPSC-derived platelets was compared to adult donor-derived platelets by profiling angiogenesis-related protein expression. Nineteen of 24 angiogenesis-related proteins were expressed equally, lower or higher in hiPSC-derived compared to adult platelets. The hiPSC-platelet's coagulation hyporeactivity compared to adult platelets was confirmed by thromboelastometry. Further stepwise improvement of hiPSC-platelet production will, thus, permit better identification of platelet-mediated regenerative mechanisms and facilitate manufacture of sufficient amounts of functional platelets for clinical application.

Placental Complement Activation in Fetal and Neonatal Alloimmune Thrombocytopenia: An Observational Study

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a disease that causes thrombocytopenia and a risk of bleeding in the (unborn) child that result from maternal alloantibodies directed against fetal, paternally inherited, human platelet antigens (HPA). It is hypothesized that these alloantibodies can also bind to the placenta, causing placental damage. This study aims to explore signs of antibody-mediated placental damage in FNAIT. We performed a retrospective study that included pregnant women, their newborns, and placentas. It comprised 23 FNAIT cases, of which nine were newly diagnosed (14 samples) and 14 were antenatally treated with intravenous immune globulins (IVIg) (21 samples), and 20 controls, of which 10 had anti-HLA-class I antibodies. Clinical information was collected from medical records. Placental samples were stained for complement activation markers (C1q, C4d, SC5b-9, and mannose-binding lectin) using immunohistochemistry. Histopathology was examined according to the Amsterdam criteria. A higher degree of C4d deposition was present in the newly diagnosed FNAIT cases (10/14 samples), as compared to the IVIg-treated FNAIT cases (2/21 samples, p = 0.002) and anti-HLA-negative controls (3/20 samples, p = 0.006). A histopathological examination showed delayed maturation in four (44%) placentas in the newly diagnosed FNAIT cases, five (36%) in the IVIg-treated FNAIT cases, and one in the controls (NS). C4d deposition at the syncytiotrophoblast was present in combination with low-grade villitis of unknown etiology in three newly diagnosed FNAIT cases that were born SGA. We conclude that a higher degree of classical pathway-induced complement activation is present in placentas from pregnancies with untreated FNAIT. This may affect placental function and fetal growth.

A case report of prenatal diagnosis of fetal alloimmune thrombocytopenia: A CARE-compliant article

RATIONALE

Fetal alloimmune thrombocytopenia (FAIT) is a serious life-threatening disease caused by platelet-antigen incompatibility between the mother and fetus. FAIT can lead to fetal thrombocytopenia, intracranial hemorrhage (ICH), fetal death and severe neurological disorders after birth. Noninvasive prenatal diagnosis technology has not been widely used in China, and thus few cases of FAIT can be diagnosed prenatally. In this study, we report a case of prenatal diagnosis and treatment of FAIT.

PATIENT CONCERNS

A 29-year-old female was admitted at 32 weeks' gestational age (GA). Fetal ultrasound at 32 weeks' GA showed a hemorrhagic focus area in the left lateral ventricle and the sign of severe fetal anemia. Hence, fetal umbilical cord puncture was ordered to identify the etiology.

DIAGNOSES

The fetal cord blood test revealed a normal hemoglobin level but severe fetal thrombocytopenia (platelet count, 23 × 109/L). Antibodies of human platelet antigens and human leukocyte antigens between mother and fetus were positive, and thus the diagnosis of FAIT was confirmed.

INTERVENTIONS

The patient refused intravenous immunoglobulin (IVIG) therapy owing to financial consideration. She was treated with dexamethasone acetate tablets (Xianju Company, China) 0.75 mg twice a day until delivery and cesarean section was performed at 34 weeks' GA. The newborn received postnatal anti-platelet antibody treatment.

OUTCOMES

The platelet count of the newborn progressively decreased until the third day after birth and it increased to normal level after postnatal treatment. The neonatal cerebral ultrasound showed the area of hemorrhage was in the process of absorption. During the postnatal one-year follow-up, the neonate showed normal developmental milestones and had no abnormal signs of neurological symptoms.

LESSONS

For FAIT, the fetal umbilical cord puncture can be carried out by skilled fetal medical teams. Dexamethasone acetate tablets can be an alternative choice for patients from underdeveloped areas.

Glanzmann Thrombasthenia: Perspectives from Clinical Practice on Accurate Diagnosis and Optimal Treatment Strategies

Glanzmann thrombasthenia (GT) is a rare autosomal recessive disorder of fibrinogen-mediated platelet aggregation due to a quantitative or qualitative deficit of the α_IIbβ₃ integrin at the platelet surface membrane resulting from mutation(s) in ITGA2B and/or ITGB3. Patients tend to present in early childhood with easy bruising and mucocutaneous bleeding. The diagnostic process requires consideration of more common disorders of haemostasis and coagulation prior to confirming the disorder with platelet light transmission aggregation, flow cytometry of CD41 and CD61 expression, and/or exon sequencing of ITGA2B and ITGB3. Antifibrinolytic therapy, recombinant activated factor VII, and platelet transfusions are the mainstay of therapy, although the latter may trigger formation of anti-platelet antibodies in GT patients and inadvertent platelet-refractory disease. The management of these patients therefore remains complex, particularly in the context of trauma, labour and delivery, and perioperative care. Bone marrow transplantation remains the sole curative option, although the venue of gene therapy is being increasingly explored as a future alternative for definitive treatment of GT.

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.

Multidisciplinary management of anti-PP1Pk or anti-P alloimmunization during pregnancy: A new case with anti-P and a literature review

BACKGROUND

Red blood cell alloimmunization is the first cause of fetal and neonatal anemia. Alloimmunizations with anti-PP1P^k or anti-P can cause recurrent miscarriages and hemolytic disease of the fetus and newborn in the 2nd and 3rd trimesters of pregnancy. We report on a pregnant patient immunized with anti-P and a history of recurrent miscarriages.

CASE REPORT

This P₂ ^k (GLOB:-1; P1PK:-1,3) patient had a first pregnancy marked by a caesarean at 38 weeks of gestation (WG) for non-reassuring fetal heart rate. Then, she had three early spontaneous miscarriages. The fifth pregnancy began with a high titer of anti-P at 128. Early initiation of treatment with Intravenous Immunoglobulins (IVIg) and plasma exchanges (PE) starting at 5 WG permitted us to reduce the titer of anti-P below 32. A healthy infant was delivered by caesarean at 38 WG without anemia at birth and no exchange transfusion was required.

DISCUSSION AND REVIEW OF THE LITERATURE

The P and P^k antigens are expressed on placental, trophoblastic, and embryonic cells. This explains why P₁ ^k (GLOB:-1; P1PK:1,3), P₂ ^k (GLOB:-1; P1PK:-1,3), or Tj(a-)/p (GLOB:-1; P1PK:-1,-3) patients are prone to recurrent abortions in the first trimester of pregnancy. A literature review demonstrated 87% (68/78) of miscarriages in p patients. However, publication biases are possible with the most severe cases being reported.

CONCLUSION

Immunizations to P and PP1P^k antigens differ from others in their physiopathology and precocity. The association of PE and IVIg seems to be an effective treatment in the management of anti-PP1P^k or anti-P fetomaternal incompatibilities.

Neonatal Alloimmune Thrombocytopenia: A Concise Review

BACKGROUND

Neonatal alloimmune thrombocytopenia (NAIT) is defined as an uncommon platelet disorder caused by maternal alloimmunization to human-specific antigens (HPAs) that are paternally inherited, resulting in low fetal/neonatal platelet levels and debilitating effects on the newborn. The incidence of NAIT is 1 in every 1000 live births within the United States; it is the most common cause of severe thrombocytopenia (<30 × 109/L) and intracranial hemorrhage in term newborns.

PURPOSE

The purpose of this article is to discuss the pathophysiology, clinical manifestations, diagnosis, and treatment of NAIT and its implications upon the lifespan of the neonate.

METHODS

A literature review was conducted using PubMed, CINAHL, and Google Scholar (2014-2019). Search terms included NAIT, neonatal/fetal alloimmune thrombocytopenia, newborn platelets, and intracranial bleeding and NAIT.

RESULTS

NAIT can affect first pregnancies and often goes undiagnosed until delivery. Universal screening tools with a focus on HPA-1a typing via noninvasive testing have been successfully trialed and have yielded promising results indicating a 75% reduction in risks associated with NAIT; however, none have been incorporated into practice and prophylactic treatment remains unavailable.

IMPLICATIONS FOR RESEARCH

Adopting a universal screening tool and prophylaxis for NAIT would allow for early diagnosis and treatment in utero.

IMPLICATIONS FOR PRACTICE

Many healthcare providers are not familiar with NAIT often focusing on other causes of thrombocytopenia as a potential diagnosis.

Update on the Use of Intravenous Immunoglobulin in Pregnancy

Intravenous immunoglobulin (IVIG) was first administered to humans in the 1980s. The mechanism of action of IVIG is still a subject of debate but the pharmacokinetics have been well characterized, albeit outside of pregnancy. IVIG has been used in pregnancy to treat several nonobstetrical and obstetrical-related conditions. However, current evidence suggests that IVIG use during pregnancy can be recommended for 1) in utero diagnosis of neonatal alloimmune thrombocytopenia; 2) gestational alloimmune liver disease; 3) hemolytic disease of the fetus and newborn for early-onset severe intrauterine disease; 4) antiphospholipid syndrome (APS) when refractory to or contraindicated to standard treatment, or in catastrophic antiphospholipid syndrome; and 5) immune thrombocytopenia when standard treatment is ineffective or rapid increase of platelet counts is needed. All recommendations are based on case series and cohort studies without randomized trials usually because of the rare prevalence of the conditions, the high incidence of adverse outcomes if left untreated, and ethical concerns. In contrast, IVIG therapy cannot be recommended for recurrent pregnancy loss, and the use of IVIG in subgroups of those with recurrent pregnancy loss requires further investigations. For non-obstetrical-related conditions, we recommend using IVIG as indicated for nonpregnant patients. In conclusion, the use of IVIG during pregnancy is an effective treatment in some obstetrical-related conditions with rare serious maternal side effects. However, the precise mechanisms of action and the long-term immunologic effects on the fetus and neonate are poorly understood and merit further investigations.

Is there a Role of Intravenous Immunoglobulin in Immunologic Recurrent Pregnancy Loss?

Recurrent pregnancy loss (RPL) commonly refers to three or more miscarriages that occur before 20 weeks of pregnancy. The immunological cause of RPL could be either an auto- or alloimmune-related event or both. Because of the discovery of immunological abnormalities in RPL patients in clinical practice, several immunomodulatory therapies were introduced to maintain the immune balance at the maternal-fetal interface. Intravenous immunoglobulin (IVIg) is one of the immunomodulators. In recent years, several studies have analyzed the therapeutic effect of IVIg on RPL patients with antiphospholipid syndrome (APS) or unexplained RPL. However, their results are controversial. IVIg can be used in RPL patients with APS who have previously failed in other treatments. It is recommended that IVIg infusion could be considered used before conception in RPL patients who have cellular immune abnormalities such as increased natural killer (NK) cell counts, NK cell cytotoxicity, or increased T helper (Th)1/Th2 ratio, depending on the cut-off values of each hospital. The aim of this review was to summarize the mechanisms, efficacy, pharmacokinetics, and side effects associated with passive immunization using IVIg in immunologic RPL, according to the literature published in recent years. We hope that more obstetricians will be able to understand the timing and indication of IVIg properly in immunologic RPL patients and effectively enhance pregnancy outcomes for mothers and neonates.

Intravenous Immune Globulin Uses in the Fetus and Neonate: A Review

Intravenous immune globulin (IVIG) is made after processing plasma from healthy donors. It is composed mainly of pooled immunoglobulin and has clinical evidence-based applications in adult and pediatric populations. Recently, several clinical applications have been proposed for managing conditions in the neonatal population, such as hemolytic disease of the newborn, treatment, and prophylaxis for sepsis in high-risk neonates, enterovirus parvovirus and COVID-19 related neonatal infections, fetal and neonatal immune-induced thrombocytopenia, neonatal hemochromatosis, neonatal Kawasaki disease, and some types of immunodeficiency. The dosing, mechanism of action, effectiveness, side effects, and adverse reactions of IVIG have been relatively well studied in adults but are not well described in the neonatal population. This review aims to provide the most recent evidence and consensus guidelines about the use of IVIG in the fetus and neonate.

Current perspective and scope of fetal therapy: part 2

Fetal therapy has been defined as any therapeutic intervention either invasive or noninvasive for correcting or treating any fetal malformation or condition. Invasive fetal therapy have its own set of maternal and fetal complications and invasive approach is not feasible in many of fetal conditions that are candidate for fetal therapy. Many such fetal conditions have been treated successfully by medical or noninvasive management. In medical fetal therapy, mothers are treated with medications which are transferred to fetus through placenta and exert positive effect on the fetus, thus avoiding complications that are seen secondary to invasive fetal therapy. The fetal conditions that have been managed with medical therapy includes fetal and neonatal alloimmune thrombocytopenia, neural tube defect, congenital adrenal hyperplasia, perinatal infections, respiratory distress syndrome, inborn error of metabolism, and congenital cystic adenomatoid malformation. This review will cover the medical or noninvasive aspect of fetal therapy and will highlight the progress made in the management of these fetal conditions.

Fetal and Neonatal Alloimmune Thrombocytopenia-New Prospects for Fetal Risk Assessment of HPA-1a-Negative Pregnant Women

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare and potentially serious bleeding condition in the fetus/newborn. FNAIT is usually considered as the platelet counterpart of hemolytic disease of the fetus and newborn. In FNAIT, maternal alloantibodies against paternally inherited platelet antigens traverse the placenta and cause thrombocytopenia in the fetus/newborn. The most common and most serious cases of FNAIT among white people are caused by alloantibodies against the human platelet antigen 1a (HPA-1a), which is absent in 2.3% of women. Today, there is no screening for FNAIT, and for this reason, FNAIT is not suspected until an otherwise healthy child, born at term, presents with thrombocytopenia. Clinical management of subsequent pregnancies at risk of FNAIT is mostly based on the obstetric history. During the last 5 decades, hemolytic disease of the fetus and newborn caused by antibodies against RhD has successfully been prevented by administration of hyperimmune anti-D IgG drug products to RhD-negative women after delivery of an RhD-positive child. Similarly, a hyperimmune anti-HPA-1a IgG (NAITgam) is under development for the prevention of HPA-1a immunization and FNAIT. If NAITgam becomes licensed for FNAIT prophylaxis and national health authorities decide to include FNAIT screening in their antenatal health care programs, it will be necessary to improve today's tools for assessing the risk of FNAIT. Although the primary risk factor for HPA-1a immunization is platelet type HPA-1bb, not all HPA-1a-negative women develop anti-HPA-1a. The women who are HLA-DRB3:01:01 negative (72%) only rarely develop anti-HPA-1a, and for those few who become HPA-1a immunized, it is quite rare to have a child with severe thrombocytopenia. Determination of fetal HPA-1 type is important because 15% of HPA-1a-negative women will carry an HPA-1a-negative fetus and therefore not be at risk of FNAIT. The severity of FNAIT seems to be associated with the level of anti-HPA-1a. Hence, in Norway, for example, an Ab threshold of 3 IU/mL is used to distinguish between low- and high-risk pregnancies. The current review will discuss to what extent these analyses, as well as determination of subtypes of anti-HPA-1a (anti-β3, anti-αIIbβ3, and anti-αvβ3) and Fc core fucosylation of anti-HPA-1a IgG, can be used as risk stratification tools.

HIP (HPA-screening in pregnancy) study: protocol of a nationwide, prospective and observational study to assess incidence and natural history of fetal/neonatal alloimmune thrombocytopenia and identifying pregnancies at risk

INTRODUCTION

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) may lead to severe fetal or neonatal bleeding and/or perinatal death. Maternal alloantibodies, targeted against fetal human platelet antigens (HPAs), can result thrombocytopenia and bleeding complications. In pregnancies with known immunisation, fetal bleeding can be prevented by weekly maternal intravenous immunoglobulin infusions. Without population-based screening, immunisation is only detected after birth of an affected infant. Affected cases that might have been prevented, when timely identified through population-based screening. Implementation is hampered by the lack of knowledge on incidence, natural history and identification of pregnancies at high risk of bleeding. We designed a study aimed to obtain this missing knowledge.

METHODS AND ANALYSIS

The HIP (HPA-screening in pregnancy) study is a nationwide, prospective and observational cohort study aimed to assess incidence and natural history of FNAIT as well as identifying pregnancies at high risk for developing bleeding complications. For logistic reasons, we invite rhesus D-negative or rhesus c-negative pregnant women, who take part in the Dutch population-based prenatal screening programme for erythrocyte immunisation, to participate in our study. Serological HPA-1a typing is performed and a luminex-based multiplex assay will be performed for the detection of anti-HPA-1a antibodies. Results will not be communicated to patients or caregivers. Clinical data of HPA-1a negative women and an HPA-1a positive control group will be collected after birth. Samples of HPA-1a immunised pregnancies with and without signs of bleeding will be compared with identify parameters for identification of pregnancies at high risk for bleeding complications.

ETHICS AND DISSEMINATION

Ethical approval for this study has been obtained from the Medical Ethical Committee Leiden-The Hague-Delft (P16.002). Study enrolment began in March 2017. All pregnant women have to give informed consent for testing according to the protocol. Results of the study will be disseminated through congresses and publication in relevant peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04067375.

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.

Fetal and neonatal alloimmune thrombocytopenia: a late or missed diagnosis disease in fetal and perinatal health-care settings

Introduction: Even though Fetal and Neonatal Alloimmune Thrombocytopenia (FNAIT) has been recognized as the main cause of primary hemorrhagic morbidity and mortality in fetuses and newborns, screening programs to detect pregnancies at risk have not yet been implemented in any country. Moreover, in spite of increased concerns about maternal, fetal and neonatal health care in general, this potentially lethal disease is still underdiagnosed. The aim of this report is to highlight the importance of considering FNAIT in fetal and perinatal health-care settings and show the usefulness of molecular tools in early diagnosis of this clinical entity.Methods: DNA was extracted from whole blood from parents and newborns; genotyping was performed by in house PCR using sequence-specific primers for typing Human Platelet Antigens (HPA)-1 to -6, -9, and -15, and with commercial HPA-TYPE (BAG HealthCare, Lich, Germany). Anti-HPA antibodies in the maternal serum were detected by the Monoclonal Antibody Solid Phase Platelet antibody Test (MASPAT). Chloroquine-treated platelets were used for the discrimination of platelet-specific antibodies from anti-HLA antibodies.Results: Patients 1 and 2 had severe thrombocytopenia due to incompatibility in HPA-1 and HPA-15, respectively. The third case was a thrombocytopenic neonate with severe bleeding complications other than ICH and in whom differential diagnosis between FNAIT and Von Willebrand congenital disease was necessary; incompatibility in HPA-15 was also demonstrated. Case 4 represents a missed diagnostic opportunity.Conclusion: This is the first report of FNAIT cases confirmed by molecular evidence and anti-HPA antibodies detection in Argentina. This report reinforces the relevance of early diagnosis of this clinical entity. Since the delay in FNAIT diagnosis could lead to severe consequences in the fetus and neonates, strategies to approach maternal, fetal, and perinatal health, as well as prevention policies aimed to reduce fetal and neonatal morbidity and mortality should focus on implementing programs to identify high-risk pregnancies and thus reduce thrombocytopenia-related complications in fetuses and newborns.

Potential of Next-Generation Sequencing in Noninvasive Fetal Molecular Blood Group Genotyping

Hemolytic disease of the fetus and newborn and fetal and neonatal alloimmune thrombocytopenia are caused by maternal antibodies against fetal alloantigens on red blood cells or platelets that are inherited from the father. After transplacental transport to the fetal circulation, antibodies of the IgG class may cause severe fetal anemia or bleeding complications. The indication for noninvasive fetal blood group genotyping is given if a clinically relevant antibody is detected in a pregnant woman and if the father is heterozygous (or unknown) for the implicated blood group allele. This mini-review will focus on the advantages and current limitations of next-generation sequencing (NGS) for noninvasive diagnosis of fetal blood groups which is, in contrast to fetal aneuploidy screening, proposed only by some research groups. Targeted massively parallel sequencing of short DNA fragments from maternal cell-free plasma samples enables counting of fetal alleles for many single nucleotide polymorphisms in parallel. This information can be utilized for estimation of the fetal fraction of cell-free DNA (cfDNA) as well as detection of the paternal blood group allele in question. Adherence to a cut-off of ≥4% fetal fraction for reporting conclusive results is recommended to avoid false-negative results due to low fetal fraction. For screening purposes of fetal RHD in RhD-negative pregnant women, real-time PCR methods are very well established. However, for diagnostic purposes, the targeted amplicon-based NGS approach has the inherent capability to estimate the fetal fraction of cfDNA. In the future, improving the accuracy of NGS by consensus sequencing of single cfDNA molecules may enable reliable fetal blood group genotyping already in the first trimester of pregnancy.

The use of IVIg in fetal and neonatal alloimmune thrombocytopenia- Principles and mechanisms

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare neonatal disorder that is caused by alloimmunization against platelet antigens during pregnancy. Although rare, affecting only 1 in 1000 live births, it can cause intracranial hemorrhage and other bleeding complications that can lead to miscarriage, stillbirth and life-long neurological complications. One of the gold-standard therapies for at risk pregnancies is the administration of IVIg. Although IVIg has been used in a variety of different disorders for over 40 years, its exact mechanism of action is still unknown. In FNAIT, the majority of its therapeutic effect is thought the be mediated through the neonatal Fc receptor, however other mechanisms cannot be excluded. Due to safety, supply and other concerns that are associated with IVIg use, alternative therapies that could replace IVIg are additionally being investigated. This includes the possibility of a prophylaxis regimen for FNAIT, similarly to what has been successfully used in hemolytic disease of the fetus and newborn for over 50 years.

Fetal and neonatal alloimmune thrombocytopenia - The Norwegian management model

In Norway, the management strategy for fetal and neonatal alloimmune thrombocytopenia (FNAIT) has for more than two decades differed from most other countries. The focus of this paper is to describe and discuss the Norwegian FNAIT management program. We recommend antenatal IVIg to women who previously have had a child with FNAIT-induced ICH, and usually not to HPA-1a alloimmunized pregnant women where a previous child had FNAIT, but not ICH. When deciding management strategy, we use not only the obstetric history but also the antenatal anti-HPA-1a antibody level as a tool for risk stratification. The Norwegian National Unit for Platelet Immunology (NNUPI) at the University Hospital of North Norway in Tromsø provides diagnostic and consulting service for the clinicians and the blood banks all over the country, and serves as a national reference laboratory for FNAIT investigations.

Epidemiology and management of fetal and neonatal alloimmune thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a disease in pregnancy characterized by maternal alloantibodies directed against the human platelet antigen (HPA). These antibodies can cause intracranial hemorrhage (ICH) or other major bleeding resulting in lifelong handicaps or death. Optimal fetal care can be provided by timely identification of pregnancies at risk. However, this can only be done by routinely antenatal screening. Whether nationwide screening is cost-effective is still being debated. HPA-1a alloantibodies are estimated to be found in 1 in 400 pregnancies resulting in severe burden and fetal ICH in 1 in 10.000 pregnancies. Antenatal treatment is focused on the prevention of fetal ICH and consists of weekly maternal IVIg administration. In high-risk FNAIT treatment should be initiated at 12-18 weeks gestational age using high dosage and in standard-risk FNAIT at 20-28 weeks gestational age using a lower dosage. Postnatal prophylactic platelet transfusions are often given in case of severe thrombocytopenia to prevent bleedings. The optimal threshold and product for postnatal transfusion is not known and international consensus is lacking. In this review practical guidelines for antenatal and postnatal management are offered to clinicians that face the challenge of reducing the risk of bleeding in fetuses and infants affected by FNAIT.

Clinical analysis of eight cases of fetal intracranial hemorrhage in pregnancy

OBJECTIVE

To explore the clinical characteristics, treatment and prognosis of fetal intracranial hemorrhage in pregnancy and to improve the level of diagnosis and treatment.

METHODS

We retrospectively analyzed the clinical data of eight cases of fetal intracranial hemorrhage in our hospital from 2014 to 2017, including the clinical manifestations, etiology, imaging features, treatment and prognosis.

RESULTS

All the cases were diagnosed by prenatal color ultrasound or magnetic resonance imaging (MRI); one of the cases had decreased fetal movements and abnormal fetal heart rate monitoring, and the remaining seven cases had no special clinical symptoms. No clear cause was found in all the cases. Two patients with grade I fetal intracranial hemorrhage and 1 patient with grade II had a cesarean delivery, and no neurological sequelae were found in these neonates after 6 months of follow-up. There was one patient with grade III and four patients with grade IV fetal intracranial hemorrhage; one of the patients with grade IV was stillborn at the time of the discovery, and cesarean section was selected due to scarring of the uterus; intra-amniotic injection of ethacridine lactate was selected to induce labor in three cases, and vaginal delivery was selected; one of the patients with grade IV chose vaginal delivery, and the neonatal cranial brain magnetic resonance imaging after delivery showed no increase in intracranial lesions but showed incomplete development of the remaining nervous system.

CONCLUSION

Fetal intracranial hemorrhage can be diagnosed by prenatal color ultrasound and MRI, yet it is often impossible to determine the cause. The prognosis of fetal intracranial hemorrhage is related to grade, and the prognosis of cerebral hemorrhage in patients with grades III-IV is poor.

Fast and low-cost direct ELISA for high-throughput serological HPA-1a typing

BACKGROUND

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is caused by maternal alloantibodies against fetal human platelet antigens (HPAs), mostly caused by anti-HPA-1a. Population-based screening for FNAIT is still a topic of debate. Logistically and financially, the major challenge for implementation is the typing of pregnant women to recognize the 2% HPA-1a-negative women. Therefore, there is need for a high-throughput and low-cost HPA-1a-typing assay.

STUDY DESIGN AND METHODS

A sandwich ELISA was developed, using a monoclonal anti-GPIIIa as coating antibody and horseradish-peroxidase-conjugated recombinant anti-HPA-1a, as detecting antibody. The ELISA results were compared to an allelic discrimination PCR-assay. In phase I, samples from unselected consecutive pregnant women were tested with both assays. Phase II was part of a prospective screening study in pregnancy and genotyping was restricted to samples with an arbitrary set, OD < 0.500.

RESULTS

The ELISA was optimized to require no additional handling (swirling or spinning) of stored tubes. During phase I, 506 samples were tested. In phase II, another 62,171 consecutive samples were phenotyped, with supportive genotyping in 1,902. In total 1,585 HPA-1a negative and 823 HPA-1a positive women were genotyped. The assay reached 100% sensitivity with a cut-off OD from 0.160, corresponding with a 99.9% specificity and a false-HPA-1a negative rate of 0.03.

CONCLUSION

A high-throughput, low-cost, and reliable HPA-1a phenotyping assay was developed which can be used in population-based screening to select samples for testing of presence of anti-HPA-1a. Because plasma from tubes of 3- to 6-days-old samples can be used, this assay is applicable to settings with suboptimal conditions.

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.

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

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