Teratogenic Medications: What You Need to Know Before Taking Them

When you're pregnant or trying to get pregnant, teratogenic medications, drugs that can cause birth defects by interfering with fetal development. Also known as fetal toxicants, these substances don't just affect you—they can change how your baby's organs, limbs, or brain form in the womb. It’s not about fear. It’s about awareness. Many common prescriptions and even over-the-counter pills can be risky if taken at the wrong time. The first trimester is the most sensitive, but risks can stretch into later months depending on the drug and how your body processes it.

Not all medications are dangerous, but some are well-documented culprits. For example, valacyclovir, the active ingredient in Valtrex, is often used for herpes outbreaks and has been studied in pregnancy with mixed results—some data suggests low risk, but caution is still advised. Then there’s ketorolac tromethamine, a strong NSAID used for post-surgery pain, which can restrict blood flow to the fetal kidneys and cause low amniotic fluid if taken after 30 weeks. Even mefenamic acid, the active ingredient in Ponstel, a common pain reliever, carries warnings for use in late pregnancy due to potential heart and kidney effects on the baby.

What you take matters, but so does timing, dosage, and your personal health history. A drug that’s safe for someone else might not be safe for you. That’s why doctors rely on pregnancy risk categories and real-world data—not just labels on bottles. You’re not alone in this. Thousands of women take necessary medications during pregnancy every year, and with the right guidance, most outcomes are healthy. The goal isn’t to avoid all meds—it’s to avoid the wrong ones at the wrong time.

Below, you’ll find real comparisons and deep dives into medications that are often questioned during pregnancy. From painkillers to antivirals, antibiotics to hormonal treatments, each post breaks down what’s known, what’s uncertain, and what you should ask your provider. No guesswork. No jargon. Just clear facts to help you make smarter choices—for your body and your baby.