HPSE and Thrombocytopenia: Testing for fetal and neonatal alloimmune thrombocytopenia (FNAIT) should be performed in any neonate with unexplained thrombocytopenia <50.000/mm3, regardless of the presumed cause.(2) Diagnosis is made by platelet genotyping showing HPA fetal-maternal incompatibility and detection of anti-HPA antibodies in the mother's serum.(1)