Thrombocytopenia occurs commonly during pregnancy, and may result from diverse etiologies. Awareness of these many causes facilitates proper diagnosis and management of thrombocytopenia in the pregnant setting. Some causes of thrombocytopenia are unique to pregnancy and may not be familiar to hematologists. In the review, we will discuss the differential diagnosis of thrombocytopenia in pregnancy, and the pathogenesis of selected thrombocytopenic disorders. Considerations for optimal management of the pregnant patient with thrombocytopenia will also be described.