Heparins are the preferred anticoagulants for managing VTE risk in pregnancy, though current clinical recommendations rely primarily on case series and expert opinion.
The purpose of this review is to summarize the epidemiology of venous thromboembolism (VTE) in pregnancy and describe strategies used to prevent and treat it. The main reason for the increased risk of VTE in pregnancy is hypercoagulability. The hypercoagulability of pregnancy, which has likely evolved to protect women from the bleeding challenges of miscarriage and childbirth, is present as early as the first trimester and so is the increased risk of VTE. Other risk factors include a history of thrombosis, inherited and acquired thrombophilia, certain medical conditions, and complications of pregnancy and childbirth. Candidates for anticoagulation are women with a current thrombosis, a history of thrombosis, thrombophilia, and a history of poor pregnancy outcome, or postpartum risk factors for VTE. For fetal reasons, the preferred agents for anticoagulation in pregnancy are heparins. There are no large trials of anticoagulants in pregnancy and recommendations are based on case series and the opinion of experts. Nonetheless, anticoagulants are believed to improve the outcome of pregnancy for women who have or have had VTE.
Allison James (2009) studied this question.