Current concepts of anticoagulant therapy in pregnancy

Pregnant women are subjected to a fivefold increased risk of venous thrombosis during pregnancy and are more likely to die from this disease after a live birth than from any other cause in the United States.(5) Thromboembolism also accounts for the largest number of maternal deaths in Wales and England,(33) and data from Sweden during the period 1980 to 1988 also confirmed embolism as the leading cause of maternal death.(56) Multiple changes in the coagulation system account for the hypercoagulable state of pregnancy, including increases in clotting factors, decreases in natural inhibitors of coagulation, changes in the fibrinolytic system, increases in venous stasis, and vascular injury at delivery from placental separation, cesarean section, or infection.(10) As a consequence, antithrombotic therapy in pregnancy is used for the treatment of acute events, the prophylaxis of patients with a history of events, the prevention and treatment of systemic embolization in women with valvular disease, and as prophylaxis against fetal loss and thrombosis in women with the antiphospholipid antibody syndrome. Despite the gravity of this problem in pregnant women, treatment guidelines are nondefinitive and often contradictory because the evidence upon which recommendations can be based is largely derived from retrospective studies. Pregnant women are usually excluded from prospective treatment studies owing to concerns that antithrombotic agents pose risks for both maternal and fetal complications. This article critically appraises the literature on the maternal and fetal effects of anticoagulants, including low-molecular-weight heparin (LMWH) and thrombolytic agents; discusses controversial guidelines from expert panels; and offers recommendations for their use in pregnancy.