[Differential diagnosis of thrombocytopenia in pregnancy]

Thrombocytopenia (< 150,000/microliter) is a common finding, occurring in 7-8% of pregnancies. Some conditions, such as gestational thrombocytopenia pose no maternal or fetal risks. Idiopathic thrombocytopenic purpura (ITP) is an acquired haematologic disorder, common among children and adults, with unknown etiology and autoimmune pathogenesis. The incidence of severe fetal and neonatal thrombocytopenia is very rare, and neonatal intracranial hemorrhage is unlikely to be related to the mode of delivery. Alloimmune thrombocytopenia occurs with an incidence of 1/1,000 livebirths and is induced by a maternal alloimmunization against fetal platelet antigens. The incidence of intracranial haemorrhage in the fetus and neonate is the highest for any immune thrombocytopenia. The HELLP syndrome is a severe, unpredictable and life-threatening complication of preeclampsia, characterized by a triad of hemolysis, elevated liver enzymes and low platelet counts. HELLP syndrome develops in the third trimester but can occur postpartum. Hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) are syndromes of microangiopathic hemolytic anemia, and thrombocytopenia. During pregnancy, TTP usually presents in the second trimester, whereas HUS develops in the postpartum period. Heparin-induced thrombocytopenia type II is a serious, immune-mediated complication of heparin therapy.