Subamniotic Hemorrhage, a Possible New Presentation of Fetal and Neonatal Alloimmune Thrombocytopenia

BACKGROUND: Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare fetal disease in which maternal antibodies directed toward fetal human platelet antigens (HPA) are formed during pregnancy and cause fetal thrombocytopenia. The diagnosis FNAIT is suspected when a fetus or neonate presents with signs of bleeding. CASE: We describe a pregnancy complicated by a placental hematoma in the 20th week of gestation as the first manifestation of FNAIT. Further evaluation showed signs of germinal matrix hemorrhage and HPA-5b allo-antibodies. After the diagnosis, intravenous immunoglobulin was administered weekly and a healthy daughter was born at 37 weeks. Histopathological analysis revealed that the hematoma was caused by a subamniotic hemorrhage of fetal origin. CONCLUSION: A subamniotic hematoma appears to be the first manifestation of FNAIT.