Clinical management in FNAIT - navigating a complicated landscape

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is the primary cause of severe neonatal thrombocytopenia and fetal/neonatal intracranial hemorrhage (ICH) in otherwise healthy term newborns. FNAIT occurs in 0.5-1:1000 newborns. FNAIT may occur if the mother and fetus have incompatible platelet antigens, leading to maternal alloimmunization with antibodies targeting the fetal platelets. The main clinical concern is the risk of ICH, with a reported incidence of 1:10,000 newborns. Most bleedings occurs prior to delivery. Due to the lack of HPA-1a screening in pregnancy, most pregnancies complicated by FNAIT are not diagnosed until after birth and the condition is underdiagnosed. Current antenatal management protocols are focused on subsequent pregnancies, when a mother has had a previously affected neonate. The primary goal of treatment during the subsequent pregnancy is to prevent ICH in the current fetus/neonate. The predicted risk of ICH in subsequent pregnancies depends mainly on whether the previous FNAIT-affected sibling had ICH or not. In most Western countries, weekly off-label administration of high-dose IVIg is used for pregnant HPA-1a-alloimmunized women to prevent ICH in the fetus/newborn. However, many experts advocate for a more stratified approach that limits which at-risk pregnancies are offered IVIg. This non-systematic expert review will focus on ante- and perinatal clinical management of FNAIT, addressing both clinical (non-screening) and screening scenarios.