Relative frequency of etiology of thrombocytopenia during pregnancy by trimester. Relative frequency estimated based on review of literature and experience as described in Cines and Levine³  includes infection, disseminated intravascular coagulation, drug-induced thrombocytopenia, and bone marrow failure.

*In a study by Reese et al,¹  1.8% of women with uncomplicated pregnancies had platelets <150 × 10⁹/L. Gestational thrombocytopenia was far more common in the second or third trimesters.