Among the medications listed for maternal cardiovascular disease, which has established teratogenic effects on the fetus?

• A. Warfarin
• B. Heparin
• C. Beta-blockers
• D. Aspirin

Answer: (A)

Warfarin's teratogenic risk comes from its ability to cross the placenta and act as a vitamin K antagonist in the fetus. By blocking vitamin K–dependent carboxylation of clotting factors II, VII, IX, and X, it can disrupt normal fetal development when exposure occurs during organ formation. This leads to fetal warfarin syndrome, characterized by nasal and midface hypoplasia, limb deformities, and skeletal or CNS abnormalities, particularly with first-trimester exposure. Because of these well-established fetal harms, warfarin is avoided in pregnancy when possible, with heparin (which does not cross the placenta) used as an alternative. Beta-blockers and aspirin are not considered fetal teratogens in the same way, though they can have other fetal risks at certain doses or with specific agents.