Which drug is definitely teratogenic

• A. Chloroquine
• B. Sulfasalazine
• C. Methylprednisolone
• D. Cyclophosphamide

Answer: (D)

Teratogens are drugs that cause birth defects when a fetus is exposed during development, especially in the first trimester when organ formation occurs. Cyclophosphamide is a classic example because it’s a potent alkylating agent that crosses the placenta and damages fetal DNA in rapidly dividing cells. This disruption during organogenesis leads to congenital anomalies, growth restriction, and increased risk of fetal loss—findings that have been well documented in humans. For this reason, it is considered definitely teratogenic and is avoided in pregnancy.

The other drugs listed do not have the same well-established fetal-teratogenic profile. Chloroquine has a long-standing safety record in pregnancy and is used for malaria and certain autoimmune conditions with relatively low risk to the fetus. Sulfasalazine is generally regarded as safe in pregnancy when accompanied by folate supplementation, though it can affect folate status if not managed. Methylprednisolone, a corticosteroid, carries potential fetal risks with high-dose exposure but is not classically labeled a definite teratogen in the way cyclophosphamide is, and may be used when benefits outweigh risks.