American Board of Internal Medicine (ABIM) Certification Practice Exam

In the first trimester, what anticoagulation approach is commonly used for patients with a mechanical valve prosthesis?

1. Weight-based LMWH

2. Discontinue all anticoagulation

3. Warfarin with a dose ≤5 mg

4. Only UFH

The correct answer is: Warfarin with a dose ≤5 mg

The correct approach for anticoagulation in patients with a mechanical valve prosthesis during the first trimester of pregnancy is the use of warfarin at a dose of 5 mg or less. This is due to the need to balance the risks of thromboembolism related to the mechanical valve with the potential teratogenic effects of anticoagulation therapy. Warfarin is effective in preventing thromboembolic events, which is especially important for patients with mechanical valves that pose a higher risk during pregnancy. Lower doses of warfarin can be used cautiously in the first trimester since there is a risk for congenital malformations associated with higher levels of the drug, but the strategy remains to maintain therapeutic levels that are adequate enough to protect against thrombosis without increasing the risk of complications such as malformations. Other anticoagulation methods, such as weight-based low molecular weight heparin (LMWH), while often used, may not provide the same level of protection against thrombotic events as warfarin, particularly in high-risk patients with mechanical valves. Discontinuing all anticoagulation is not advisable as it significantly increases the risk of valve thrombosis. Similarly, unfractionated heparin (UFH) may be less practical or