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.
The management of pregnant women with prosthetic heart valves is a clinical challenge
No clear consensus exists on the optimal artificial valve and anticoagulation strategy for these women, owing to the paucity of data that can guide therapeutic decisions
Cardiac and obstetric care teams need to work collaboratively to help these patients make personalized decisions that consider the risks and benefits of various therapies
Consistent monitoring to maintain effective anticoagulation is crucial, regardless of the chosen treatment strategy
Warfarin throughout pregnancy might be appropriate for selected patients, particularly those at increased risk of thromboembolism and when the risk of adverse fetal outcomes is comparatively low
Heparin derivatives pose no direct risk to the fetus, but are limited by an appreciable risk of maternal thromboembolic complications, even in patients with seemingly therapeutic levels of anticoagulation
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The authors declare no competing financial interests.
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Castellano, J., Narayan, R., Vaishnava, P. et al. Anticoagulation during pregnancy in patients with a prosthetic heart valve. Nat Rev Cardiol 9, 415–424 (2012) doi:10.1038/nrcardio.2012.69
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