During pregnancy, women have a 4- to 5-fold increased risk of thromboembolism. Candidates for anticoagulation in pregnancy include women with current thrombosis, a history of thrombosis, risk factors for postpartum thrombosis, and some women with thrombophilia and a history of poor pregnancy outcome. Although, there are no large trials of anticoagulants in pregnancy and recommendations for their use are based on case series and the opinion of experts, observational studies demonstrate the benefit of heparins in reducing the risk of recurrent thromboembolism in pregnancy. A practical approach to the prevention and treatment of thromboembolism in pregnancy is outlined.