Effective anticoagulation is mandatory for pregnant women with mechanical heart valves. Oral
anticoagulants offer the best maternal protection against
thrombosis, but their use might be associated with an appreciable risk of
fetal malformations and pregnancy loss. By contrast,
heparin derivatives are associated with a reduced risk of fetal damage, but an increased risk of valve
thrombosis in the mother, even with appropriate dose adjustment and monitoring of therapeutic efficacy. Given the varying risks of available anticoagulation strategies, and the paucity of data to inform the optimal approach, no single accepted treatment option exists for pregnant women with mechanical prosthetic valves. Although
low-molecular-weight heparin is considered more efficacious than
unfractionated heparin, treatment failures, even at therapeutic levels of
factor Xa inhibition, have been reported. The risk of
warfarin-related
embryopathy might be overstated, particularly at doses ≤ 5 mg daily. We advocate an individualized anticoagulation strategy that takes into account the patient's preferences, calls for the use of
vitamin K antagonists throughout pregnancy (substituted with a
heparin derivative only close to term) for those patients at the greatest risk of
thromboembolism, and relies on close multidisciplinary collaboration between the cardiac and obstetric care teams.