Idiopathic thrombocytopenic purpura (ITP) is a condition that often develops in young women, and, consequently, physicians will frequently manage pregnant patients with this disorder. The lack of prospective trials investigating ITP in pregnancy has meant that physicians frequently rely on personal experience and anecdotal evidence to manage these patients. However, recent, large, prospective and retrospective studies have clarified several important aspects of ITP in pregnancy. First, ITP should be distinguished from incidental thrombocytopenia of pregnancy, a high frequency and benign, mild drop in the platelet count that occurs late in pregnancy. Second, although the platelet count often drops in pregnant ITP patients, serious morbidity or mortality is distinctly uncommon for the mothers. The overall frequency of thrombocytopenia in the infant is quite low, and about 5% of infants will have a birth platelet count less than 20 x 10(9)/L and about 1% will have significant bleeding complications.