Which medication is advised to avoid during the first trimester due to the risk of NTDs?

The correct medication to avoid during the first trimester due to the risk of neural tube defects (NTDs) is trimethoprim/sulfamethoxazole. This combination antibiotic contains trimethoprim, which is a folate antagonist. During the critical period of embryonic development, specifically in the first trimester, folate is essential for proper neural tube formation. The use of folate antagonists can interfere with this critical process, increasing the risk of NTDs such as spina bifida and anencephaly.

In contrast to trimethoprim/sulfamethoxazole, metformin, lisinopril, and amoxicillin are generally considered safer options during early pregnancy. Metformin is often used in women with gestational diabetes or polycystic ovary syndrome and has not been associated with an increased risk of NTDs. Lisinopril, an angiotensin-converting enzyme (ACE) inhibitor, is typically avoided after the first trimester, but its neural tube teratogenicity primarily concerns the second and third trimesters. Amoxicillin is a penicillin antibiotic that is considered safe to use during pregnancy and does not have a known association with NTDs.

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