Okay, let's tackle this question. The user provided a question about antitubercular drugs in pregnancy but didn't list the options. Hmm, that's a bit tricky. But maybe the correct answer is a drug known to be contraindicated during pregnancy.

First, the core concept here is the safety of antitubercular drugs during pregnancy. The main concern is the potential teratogenicity or harm to the fetus. I remember that some drugs like rifampin are considered safe, but others might not be. Wait, what about pyrazinamide? Oh, there's some debate there. But the big one is probably ethambutol. Wait, no, ethambutol is safe. Oh, wait, streptomycin? Wait, streptomycin is an aminoglycoside and can cause ototoxicity in the fetus. But I think the main one is ethionamide. Or maybe capreomycin? Wait, maybe it's ethambutol? No, ethambutol is safe. Let me think again. The standard first-line drugs are isoniazid, rifampin, pyrazinamide, and ethambutol. Isoniazid is category B, rifampin is category C, pyrazinamide is category B, and ethambutol is category C. But wait, some sources say that pyrazinamide has limited data in pregnancy. However, in practice, the first-line drugs are considered safe except for streptomycin and other aminoglycosides. Wait, maybe the question is about a drug that's contraindicated. Let me recall: ethionamide is a second-line drug and is teratogenic. Oh right, ethionamide is contraindicated in pregnancy because it's an antifolate, which can cause neural tube defects. So if the options include ethionamide, that would be the answer. Alternatively, maybe capreomycin? No, capreomycin is a polypeptide antibiotic and is used in pregnancy. Wait, but the question is about which should not be used. So the answer is ethionamide. Let me check: Ethionamide is contraindicated in pregnancy due to its teratogenic potential. So if the options include ethionamide, then that's the correct answer. The other options would be the first-line drugs like INH, RIF, PZA, and EMB. So the correct answer would be ethionamide. Therefore, the correct answer is the option that lists ethionamide. So the explanation would need to cover why ethionamide is contraindicated, and the others are safe. The core concept is the safety of antitubercular drugs during pregnancy. The clinical pearl is that ethionamide is contraindicated due to teratogenicity. The wrong options would be the first-line drugs which are safe. So the answer is ethionamide.

**Core Concept**
The safety of antitubercular drugs during pregnancy hinges on their teratogenic potential and fetal toxicity. Ethionamide, a second-line antitubercular agent, is contraindicated due to its antifolate mechanism, which disrupts folate metabolism and increases neural tube defect risk.

**Why the Correct Answer is Right**
Ethionamide is contraindicated in

✓ Correct Answer: C. Streptomycin