**Core Concept**
Phocomelia is a congenital anomaly characterized by the shortening or absence of limbs, often associated with exposure to certain teratogenic agents during fetal development. Thalidomide, a sedative and antiemetic, was widely used during the 1950s and 1960s, but its use was discontinued due to its severe teratogenic effects.

**Why the Correct Answer is Right**
Thalidomide works by inhibiting the synthesis of prostaglandins, which are essential for normal limb development. When a pregnant woman takes thalidomide, it crosses the placenta and binds to the prostaglandin synthase enzyme, preventing the formation of prostaglandins. This disruption in prostaglandin synthesis leads to the characteristic limb deformities seen in phocomelia. The affected limbs fail to develop properly, resulting in shortening or absence of the limbs.

**Why Each Wrong Option is Incorrect**
* **Option A:** Thalidomide's mechanism of action does not involve the inhibition of prostaglandin synthesis, making this option incorrect.
* **Option B:** Thalidomide is not known to cause cleft palate, a different congenital anomaly. This option is incorrect due to the lack of association with the correct condition.
* **Option C:** Thalidomide's teratogenic effects are not related to its antihistamine properties, making this option incorrect.

**Clinical Pearl / High-Yield Fact**
Thalidomide's severe teratogenic effects led to its withdrawal from the market in the 1960s, and it has since been used cautiously in the treatment of certain cancers and multiple myeloma. However, its use in pregnant women is strictly contraindicated due to the risk of severe congenital anomalies.

**Correct Answer:** C. Thalidomide.