Fetal and neonatal alloimmune thrombocytopenia (FNAIT): Survey of UK fetal medicine centres on antenatal management of subsequent affected pregnancies.

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare condition associated with severe fetal thrombocytopenia and intracerebral haemorrhage. Antenatal management of subsequent pregnancies relies on intravenous immunoglobulin (IVIg); yet, practice varies internationally and UK data are limited. We conducted a national survey to characterise the current antenatal management of FNAIT across UK regional fetal medicine centres using an electronic, scenario-based design. Responses were analysed descriptively, with ≥75% concordance considered strong agreement. Sixteen of 22 regional fetal medicine centres (73%) responded; all respondents were fetal medicine specialists or haematologists. There was strong consensus to treat standard- and high-risk pregnancies associated with anti-human platelet antigen (HPA)1a or anti-HPA5b antibodies using weekly IVIg, most commonly at a dose of 1 g/kg/week. Earlier initiation of IVIg was favoured for high-risk pregnancies, while timing was more variable for standard-risk cases. Corticosteroids were not routinely used in standard-risk pregnancies but were considered in high-risk scenarios. Fetal blood sampling and intrauterine platelet transfusion were generally avoided. Considerable variation was observed in delivery planning and in the management of pregnancies at risk without a prior confirmed diagnosis. This survey demonstrates the areas of both consistency and variation in UK practice, highlighting gaps in the evidence base and priorities for future research and guidelines development.