Mode of Birth and Bleeding Outcomes in Pregnancies at Risk of Fetal and Neonatal Alloimmune Thrombocytopenia: A Retrospective Cohort Study

Objective To assess the impact of vaginal deliveries on the occurrence of intracranial haemorrhage (ICH) in subsequent pregnancies with Fetal and Neonatal Alloimmune Thrombocytopenia (FNAIT). Design Retrospective data collection. Setting Sanquin Diagnostic Services, the national institute for diagnostic FNAIT‐testing and Leiden University Medical Center, the national referral centre for FNAIT‐management. Population 73 subsequent pregnancies with FNAIT; 16 high‐risk and 57 standard‐risk. Methods All women with a confirmed index pregnancy with alloantibodies against human platelet antigens (HPA) and a subsequent HPA‐incompatible pregnancy between March 1992 and February 2026 were included. Main Outcome Measures Severe bleeding or other bleeding symptoms in neonates, associated with mode of birth. Results There were 63 index pregnancies and 73 subsequent pregnancies, of which 72 (99%) received weekly intravenous immunoglobulin (IVIG). In the high‐risk group ( n = 16), there were 10 caesarean sections, of which four neonates had a platelet count below 50 × 10 9 /L. Of the six vaginal deliveries, two neonates had a platelet count below 50 × 10 9 /L. There were no bleeding complications. In the standard‐risk group ( n = 57), there were 19 caesarean sections of which eight neonates had a platelet count below 50 × 10 9 /L. One ICH was identified antenatally before IVIG initiation, and three neonates developed petechiae or haematomas. Of 38 vaginal deliveries, 13 neonates had a platelet count below 50 × 10 9 /L and one neonate developed petechiae. Overall (standard‐ or high‐risk), no ICH was detected in neonates delivered vaginally ( n = 44). Conclusion No ICH was observed in HPA‐alloimmunised women who had a vaginal delivery and antenatally treated with IVIG.