Key Points• The systematic review suggests that first-line antenatal management in FNAIT is weekly IVIG administration.• Noninvasive management is effective without the relatively high rate of adverse outcomes seen in invasive strategies.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. (Blood. 2017;129(11):1538-1547

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a relatively rare but potentially lethal disease, leading to severe bleeding complications in 1 in 11.000 newborns. It is the leading cause of thrombocytopenia in healthy term-born neonates. Areas covered: This review summarizes the antenatal as well as postnatal treatment, thus creating a complete overview of all possible management strategies for FNAIT. Expert commentary: The optimal antenatal therapy in order to prevent bleeding complications in pregnancies complicated by FNAIT is non-invasive treatment with weekly intravenous immunoglobulin (IVIG). Based on risk stratification, weekly doses of IVIG of 0.5 or 1.0g/kg should be administered started early in the second in high risk cases or at the end of the second trimester in low risk cases. The optimal postnatal treatment depends on the platelet count and the clinical condition of the newborn. Prompt administration of compatible platelet transfusion is the first treatment of choice in case of severe thrombocytopenia or active bleeding. In case matched platelets are not directly available, random platelets can also be administered initially to gain time until matched platelets are available. In case of persistent thrombocytopenia despite transfusions, IVIG 1.0-2.0g/kg can be administered.

Bleeding complications other than ICH may be more extensive, and the presentation of FNAIT may have a greater spectrum than previously described. A high index of suspicion on the possible diagnosis of FNAIT with any bleeding complication in a fetus or neonate may enable adequate diagnostics, adequate treatment, and appropriate follow-up in future pregnancies, as is especially relevant for FNAIT.

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.

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Objectives: To evaluate the perinatal and long-term neurodevelopmental outcome in a cohort of children with intracranial haemorrhage (ICH) due to fetal and neonatal alloimmune thrombocytopenia (FNAIT) and to clearly outline the burden of this disease. Subjects and Methods: We performed an observational cohort study and included all consecutive cases of ICH caused by FNAIT from 1993 to 2015 at Leiden University Medical Centre. Neurological, motor, and cognitive development were assessed at a minimum age of 1 year. The primary outcome was adverse outcome, defined as perinatal death or severe neurodevelopmental impairment (NDI). Severe NDI was defined as any of the following: cerebral palsy (Gross Motor Function Classification System [GMFCS] level ≥II), bilateral deafness, blindness, or severe motor and/or cognitive developmental delay (<–2 SD). Results: In total, 21 cases of ICH due to FNAIT were included in the study. The perinatal mortality rate was 10/21 (48%). Long-term outcome was assessed in 10 children (n = 1 lost to follow-up). Severe and moderate NDI were diagnosed in 6/10 (60%) and 1/10 (10%) of the surviving children. The overall adverse outcome, including perinatal mortality or severe NDI, was 16/20 (80%). Conclusions: The risk of perinatal death or severe NDI in children with ICH due to FNAIT is high. Only screening and effective preventive treatment can avoid this burden.

Summary Fetal neonatal alloimmune thrombocytopenia (FNAIT) is caused by maternal alloantibodies directed against the human platelet antigens (mostly HPA‐1a or HPA‐5b) of the (unborn) child and can lead to severe bleeding. Anti‐HPA‐1a‐mediated FNAIT shows a severe clinical outcome more often than anti‐HPA‐5b‐mediated FNAIT. Given the relatively high prevalence of anti‐HPA‐5b in pregnant women, the detection of anti‐HPA‐5b in FNAIT‐suspected cases may in some cases be an incidental finding. Therefore we investigated the frequency of anti‐HPA‐5b‐associated severe bleeding in FNAIT. We performed a retrospective nationwide cohort study in cases with clinical suspicion of FNAIT. HPA antibody screening was performed using monoclonal antibody‐specific immobilisation of platelet antigens. Parents and neonates were typed for the cognate antigen. Clinical data were collected by a structured questionnaire. In 1 864 suspected FNAIT cases, 161 cases (8·6%) had anti‐HPA‐1a and 60 (3·2%) had anti‐HPA‐5b. The proportion of cases with severe bleeding did not differ between the cases with anti‐HPA‐1a (14/129; 11%) and anti‐HPA‐5b (4/40; 10%). In multigravida pregnant women with a FNAIT‐suspected child, 100% (81/81) of anti‐HPA‐1a cases and 79% (38/48) of anti‐HPA‐5b cases were HPA‐incompatible, whereas 86% and 52% respectively were expected, based on the HPA allele distribution. We conclude that anti‐HPA‐5b can be associated with severe neonatal bleeding symptoms. A prospective study is needed for true assessment of the natural history of anti‐HPA‐5b mediated FNAIT.

In pregnancies with FNAIT with a previous affected child without ICH, treatment with IVIG in a weekly dose of 0.5 or 1.0 g/kg results in comparable neonatal PLT count at birth and degree of thrombocytopenia.