Pregnancy is associated with physiologic and non-physiologic changes in hematologic parameters. Physiologic anemia occurs due to high plasma volume. Gestational thrombocytopenia may occur due to increases in plasma volume and sequestration of platelets in the placenta. Elevation in fibrinogen and many coagulation factors favoring a procoagulant state physiologically occur during pregnancy to reduce bleeding risk with delivery. In addition, many non-physiologic hematologic changes may manifest during pregnancy due either to pre-existing hematologic diseases, or to conditions acquired during pregnancy or peripartum. Iron deficiency anemia due to pre-existing iron depletion in women of childbearing age and increased iron requirement during pregnancy is the most common cause of anemia during pregnancy. Thrombocytopenia during pregnancy may be due to immune thrombocytopenia (ITP), disseminated intravascular coagulation (DIC), HELLP syndrome, preeclampsia, and acute fatty liver of pregnancy. Congenital and acquired bleeding disorders may increase the risk of excessive bleeding. Predicting severe peripartum and postpartum hemorrhage based on hemostatic changes in women experiencing excessive bleeding and determining active hemostatic management can improve outcomes and reduce mortality