**Question:** Drugs contraindicated in pregnancy are all EXCEPT

A. **Option A:** Thalidomide
B. **Option B:** Nifedipine
C. **Option C:** Streptomycin
D. **Option D:** Methotrexate

**Core Concept:** Contraindicated drugs in pregnancy refer to medications that are explicitly not advised during pregnancy due to potential harm to the developing fetus. This could include teratogenic (causing birth defects), embryotoxic (harmful to embryos), or fetotoxic (harmful to fetuses) effects.

**Why the Correct Answer is Right:** Thalidomide is a well-known example of a drug with severe teratogenic effects, causing a variety of birth defects, including phocomelia (extremity malformations). Nifedipine is a calcium channel blocker used for hypertension management, but it can potentially cross the placenta and cause fetal bradycardia or hypotension. Streptomycin is an effective antibiotic but has been associated with hearing loss in newborns due to its potential ototoxicity. Methotrexate is a chemotherapeutic agent that can cause severe fetal toxicity and has been linked to premature closure of the fetal epiphysis, leading to bone deformities and growth abnormalities.

**Why Each Wrong Option is Incorrect:**

A. Thalidomide is a clear example of a drug with severe teratogenic effects, making it the correct answer to exclude.
B. Nifedipine is contraindicated due to potential fetal effects, but it is not as strongly associated with severe fetal harm as the other options.
C. Streptomycin is contraindicated due to its ototoxicity causing fetal hearing loss, but it is not as strongly associated with severe fetal harm as the other options.
D. Methotrexate is a chemotherapeutic agent with severe fetal toxicity and is strongly contraindicated during pregnancy.

**Clinical Pearl:** In clinical practice, it is crucial to carefully consider drug contraindications during pregnancy. Adequate knowledge of the potential risks associated with medications can help prevent iatrogenic harm to the fetus and optimize maternal and fetal safety. Always consult clinical guidelines, patient's medical history, and involve a physician with expertise in obstetrics and gynecology when deciding on drug therapy during pregnancy.