**Core Concept**
Warfarin, a commonly used oral anticoagulant, crosses the placenta and can cause embryopathy when taken during the first trimester of pregnancy. This condition is known as fetal warfarin syndrome.

**Why the Correct Answer is Right**
Warfarin inhibits vitamin K-dependent carboxylation of clotting factors, leading to an increased risk of bleeding. However, in the fetus, warfarin can also affect bone and cartilage development, causing nasal hypoplasia, stippled epiphyses, and limb abnormalities. This is due to the inhibition of vitamin K-dependent proteins involved in bone mineralization.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not mentioned in the context of warfarin embryopathy.
* **Option B:** While coumarins can cause bleeding, they do not specifically cause the congenital malformations associated with warfarin use in pregnancy.
* **Option D:** This option does not relate to warfarin embryopathy.

**Clinical Pearl / High-Yield Fact**
Warfarin embryopathy can occur with warfarin use during the first trimester, but the risk decreases significantly after this period. The American College of Obstetricians and Gynecologists (ACOG) recommends avoiding warfarin during pregnancy.

**Correct Answer: C. Warfarin embryopathy.**