Teratogenicity: What Drugs Can Cause Birth Defects and How to Stay Safe

When we talk about teratogenicity, the ability of a substance to interfere with fetal development and cause birth defects. Also known as fetal toxicity, it’s not just about obvious drugs—it’s about everyday pills, supplements, and even over-the-counter remedies that might seem harmless. A baby’s organs form in the first 8 to 12 weeks of pregnancy, and during that time, even small exposures to certain chemicals can lead to serious, lifelong problems. This isn’t science fiction. It’s documented. Thalidomide in the 1950s caused limb deformities in thousands of babies. Accutane (isotretinoin) for acne still carries strict warnings because it can cause heart defects, brain abnormalities, and facial malformations. These aren’t rare cases—they’re warning signs we can’t ignore.

Teratogenicity doesn’t just come from prescription drugs. Some herbal supplements, high-dose vitamins like vitamin A, and even certain antibiotics can be risky. For example, valproic acid, a mood stabilizer used for epilepsy and bipolar disorder, is strongly linked to neural tube defects and lower IQ in children. ACE inhibitors, common blood pressure medications, can cause kidney damage and skull deformities if taken during the second and third trimesters. Even something as simple as ibuprofen, if taken late in pregnancy, can reduce amniotic fluid and affect fetal heart function. The problem isn’t always the drug itself—it’s timing, dosage, and whether the person knows they’re pregnant.

What makes teratogenicity so tricky is that many women don’t realize they’re pregnant until after the critical window has passed. That’s why it’s not enough to stop risky medications once you see a positive test. If you’re trying to get pregnant—or could get pregnant—you need to review every medication you take with your doctor, including vitamins, painkillers, and acne treatments. Some drugs are safe to use before conception but dangerous after. Others need to be switched to safer alternatives weeks before you try to conceive. And yes, this includes birth control pills, because if you miss a pill or take it inconsistently, pregnancy can happen without warning.

There’s no magic checklist for every drug, but there are clear patterns. Medications that affect cell growth, hormone levels, or DNA replication are the biggest red flags. Cancer drugs, antiseizure meds, and some psychiatric medications top the list. But so do some common ones—like retinoids, certain antifungals, and even high-dose aspirin. The good news? Many conditions can be managed safely during pregnancy with the right alternatives. For example, insulin is safe for diabetes. Some antidepressants like sertraline have much lower risk than others. And folic acid, taken before and during early pregnancy, can cut the risk of neural tube defects by up to 70%.

What you’ll find in the articles below isn’t just a list of dangerous drugs. It’s a practical guide to navigating real-world choices. You’ll see how drug interactions like those between SSRIs and NSAIDs can affect pregnancy outcomes, how medication disposal matters even before conception, and why some treatments for chronic conditions like fatty liver disease or diabetes need to be rethought before you get pregnant. These aren’t abstract warnings—they’re daily decisions that shape a child’s health before they’re even born.