Thrombocytopenia occurring during pregnancy is a common diagnostic and management problem and may have many causes (table 1) The most common of these, along with their manifestations, are shown in the table (table 2). Asymptomatic thrombocytopenia is observed near term in about 5 percent of normal pregnancies, and thrombocytopenia, sometimes severe, develops in about 15 percent of women with preeclampsia , which itself occurs in about 3 to 4 percent of pregnancies in the United States (table 3) . The diagnosis and management of thrombocytopenia in pregnancy will be discussed here . This discussion will focus on two issues:
●Thrombocytopenia discovered incidentally during a normal pregnancy and its distinction from immune thrombocytopenia (ITP)
●Thrombocytopenia associated with preeclampsia/eclampsia and the HELLP syndrome and their distinction from thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP-HUS)
An overall approach to the patient with thrombocytopenia is discussed separately. (See "Approach to the adult patient with thrombocytopenia" and "Evaluation and management of thrombocytopenia by primary care physicians".)
Platelet counts are within the normal range of 150,000 to 450,000/microL in the vast majority of women during normal pregnancies, however they may be slightly lower, on average, than in healthy, nonpregnant women [4-6].