Validity of intrapartum diagnosis of fetal thrombocytopenia.

Performing a platelet count in fetal scalp blood was hitherto the only method to predict whether the infant of a mother with idiopathic thrombocytopenic purpura will be thrombocytopenic. Fifteen such cases are reported. Falsely low platelet counts were found in almost half of these fetal scalp samples. In two patients this could have altered the obstetric management.