Maternal–fetal platelet alloimmunization: Identification of risk factors for severe neonatal thrombocytopenia

BACKGROUND: Feto-maternal platelet alloimmunization (FNAIT) is a rare condition (1 in 1500 live pregnancies), most commonly diagnosed based on clinical neonatal hemorrhagic manifestations, which can vary in severity. The aim of our study was to identify risk factors for severe fetal/neonatal thrombocytopenia in cases of FNAIT. MATERIALS AND METHODS: A retrospective study from 1993 to 2022 of pregnancies characterized by FNAIT. Data collected included patient characteristics, management of the pregnancies, and neonatal characteristics. Comparisons regarding pregnancy management and neonatal data were made between "index cases" and "subsequent pregnancies," as well as between neonates with severe thrombocytopenia and those with no thrombocytopenia or moderate thrombocytopenia. RESULTS: Seventy-one patients were included in our study, corresponding to 119 pregnancies. Mothers of neonates with severe thrombocytopenia had a higher history of previous pregnancies characterized by severe neonatal thrombocytopenia (100.0% vs. 75.9%, p = .03). The FNAIT mainly involved the anti-HPA-1a system (75.0% vs. 54.5%, p = .02), and fewer treatments with IVIG were administered during pregnancy (6.6% vs. 34.1%, p < .001). CONCLUSION: FNAIT must be identified and appropriately managed to limit its potentially dramatic consequences, including fetal/neonatal death. Based on the patient's history, risk stratification for the occurrence of severe FNAIT in future pregnancies should be performed to tailor its management accordingly.