Fetal and neonatal alloimmune thrombocytopenia (FNAIT): A novel management strategy

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) arises from maternal-fetal platelet incompatibility, where maternal alloantibodies-most commonly anti-HPA-1a in Caucasians-cross the placenta and trigger fetal platelet destruction. The most severe complication is intracranial hemorrhage (ICH), which can occur in utero. Despite its severity, significant heterogeneity exists among national and international management guidelines.

To align clinical practice with recent evidence, the Leiden University Medical Center and Sanquin Diagnostic Services (Netherlands) revised the national FNAIT management protocol. We collected existing national and international guidelines and compared the content of the FNAIT-guidelines and published protocols regarding diagnostic tools, antenatal management, delivery, and postnatal management. Consensus was reached through a series of multidisciplinary meetings and expert panel discussions.

The novel management strategy introduces a personalized, risk-stratified framework. Pregnancies are classified into three categories: high-risk (previous FNAIT with ICH), standard-risk (previous FNAIT without ICH), and undifferentiated risk (identified incidentally or via screening). A central feature of the novel approach is the use of anti-HPA-1a antibody quantification to guide intervention; IVIg treatment is now initiated when levels exceed 2 IU/mL in both the standard-risk and undifferentiated risk groups. Additionally, the mode of delivery is determined by obstetric history, prioritizing (induced) vaginal delivery for patients with a history of uncomplicated vaginal birth.

This novel strategy provides a tailored approach to FNAIT management. By incorporating a specific anti-HPA-1a antibody cut-off, this approach aims to optimize clinical outcomes, reduce IVIg overtreatment, and support the safety of vaginal deliveries in appropriately selected patients.