When you’re pregnant, every pill, drop, or supplement feels like a gamble. You want to feel better-whether it’s for a headache, nausea, or anxiety-but you’re terrified of hurting your baby. The truth is, medication safety during pregnancy isn’t black and white. Some drugs are clearly dangerous. Others are safe. And for many, we just don’t know for sure. What’s clear is this: untreated illness can be just as risky as the medicine itself.

What Exactly Is a Teratogen?

A teratogen is any substance that can interfere with how a baby develops in the womb. This includes certain medications, alcohol, tobacco, infections like rubella, and even some environmental chemicals. The most famous example? Thalidomide. In the late 1950s, this sedative was given to pregnant women for morning sickness. By the time it was pulled from shelves in 1961, around 10,000 babies had been born with severe limb defects-some born with arms or legs that didn’t fully form. That tragedy changed how we test drugs for pregnancy safety forever.

Today, we know that about 2-3% of all birth defects are linked to medications taken during pregnancy. That sounds low, but when you’re the one taking the pill, it feels huge. The real question isn’t just “Is it safe?” It’s: “What’s the risk if I take it-and what’s the risk if I don’t?”

When Does the Risk Happen?

Not all stages of pregnancy carry the same danger. The first 12 weeks-especially days 15 to 60 after conception-are the most sensitive. That’s when your baby’s organs are forming: the heart, brain, limbs, eyes, ears. If a drug disrupts that process, it can cause major structural defects.

After week 12, the risk of major malformations drops. But that doesn’t mean you’re safe. Medications taken in the second trimester can still affect brain development, growth, or organ function. In the third trimester, drugs might cause withdrawal symptoms in the newborn, affect lung development, or trigger early labor.

Here’s how medications can hurt a developing baby:

• Direct damage: The drug crosses the placenta and directly interferes with cell growth (like methotrexate or isotretinoin).
• Indirect harm: The drug lowers your blood pressure so much that less oxygen and nutrients reach the baby.
• Placental disruption: Some drugs change how the placenta works, reducing its ability to protect or feed the baby.
• Uterine contractions: Certain meds can trigger early labor or miscarriage.
• No effect: About 60-70% of medications have no known impact on the fetus. That’s the good news.

Medications With Proven Teratogenic Risks

Some drugs are known to be dangerous-and you should avoid them entirely if you’re pregnant or trying to conceive.

• Warfarin: This blood thinner can cause fetal warfarin syndrome-nose deformities, bone problems, vision loss, and developmental delays. The risk is highest in the first trimester.
• Methotrexate: Used for autoimmune diseases and cancer, it blocks folate, which is critical for neural tube development. Exposure in early pregnancy raises the risk of neural tube defects by 10-20%.
• Carbamazepine: An epilepsy drug that increases the chance of spina bifida and other neural tube defects by about 1%. It also lowers vitamin K, which can cause dangerous bleeding in newborns.
• Factor Xa inhibitors (rivaroxaban, apixaban, edoxaban): These newer blood thinners cross the placenta, have no antidote, and lack enough human safety data. Avoid them.
• THC (cannabis): Not just a “natural” remedy. THC crosses the placenta and has been linked to low birth weight, preterm birth, stillbirth, and long-term issues like poor attention, hyperactivity, and lower IQ scores in children.

The Acetaminophen Debate: Why Experts Are Split

This is where things get messy. Acetaminophen (also called paracetamol) is the go-to painkiller for pregnant women. It’s in dozens of over-the-counter cold and flu meds. For decades, it was considered the safest option.

But in recent years, some studies have linked long-term acetaminophen use during pregnancy to a slightly higher risk of ADHD and autism in children. The CDC says these studies show an “association,” not proof of cause. Still, it’s enough to make people nervous.

Then in September 2025, the American College of Obstetricians and Gynecologists (ACOG) came out strongly in favor of acetaminophen. Their statement was clear: “The conditions people use acetaminophen to treat-like fever and pain-are far more dangerous than any theoretical risks.” Untreated fever during early pregnancy, for example, increases the risk of neural tube defects by 20-30%.

So what’s the real takeaway? If you need it for a headache, fever, or back pain, take it. Use the lowest dose for the shortest time. Don’t panic. But don’t take it daily just because you can. The risk isn’t zero-but the risk of not treating pain or fever? Much higher.

The New FDA Labeling System (PLLR)

You might remember those old pregnancy risk categories: A, B, C, D, X. They were simple-but misleading. A Category C drug didn’t mean “maybe dangerous.” It just meant “animal studies showed harm, but human data was lacking.” Many doctors still use these labels out of habit.

Since 2015, the FDA switched to the Pregnancy and Lactation Labeling Rule (PLLR). Now, prescription labels include detailed sections:

• Pregnancy: What the data says, when the risk is highest, and what to watch for.
• Lactation: Does it pass into breastmilk? Is it safe for the baby?
• Females and Males of Reproductive Potential: Does it affect fertility or require contraception?

The goal? More clarity. Less guesswork. But here’s the problem: only about 20-30% of medications have enough human data to make solid conclusions. For most, we’re still working with animal studies and case reports.

What Should You Do Before and During Pregnancy?

If you’re planning to get pregnant, don’t wait until you’re pregnant to think about meds. About half of all pregnancies are unplanned. By the time you find out, you may have already taken something risky.

Here’s your action plan:

1. Review all your meds with your doctor. This includes prescriptions, OTC drugs, supplements, and herbal remedies. Even “natural” products like St. John’s wort or high-dose vitamin A can be dangerous.
2. Switch to safer alternatives if possible. For example, if you’re on a blood pressure med that’s risky, your doctor might switch you to methyldopa or labetalol-both well-studied and safe in pregnancy.
3. Don’t stop meds cold turkey. Stopping seizure meds, antidepressants, or insulin can be more dangerous than keeping them. Work with your team to make changes safely.
4. Use trusted resources. MotherToBaby (run by teratology experts) and LactMed (from the NIH) give free, science-based advice. Avoid random blogs or Reddit threads.
5. Keep a medication log. Write down what you took, when, and why. This helps your doctor assess risk if something goes wrong.

What About Mental Health Medications?

Depression and anxiety don’t disappear during pregnancy. In fact, untreated mental illness increases the risk of preterm birth, low birth weight, and postpartum complications.

Some SSRIs like sertraline and citalopram are considered low-risk during pregnancy. Others, like paroxetine, are linked to a small increase in heart defects. But here’s the key: the risk of relapse if you stop your medication is often higher than the risk of the drug itself.

ACOG and the American Psychiatric Association both say: “The benefits of treating maternal mental illness typically outweigh the potential risks of medication.” Talk to your psychiatrist and OB-GYN together. Don’t go it alone.

When You’ve Already Taken a Risky Medication

You took ibuprofen last week before you knew you were pregnant. You used a topical retinoid. You didn’t realize your epilepsy drug was risky. Now you’re terrified.

First: Breathe. Most exposures don’t cause harm. Second: Call MotherToBaby. They’re a free, confidential service staffed by specialists who’ve handled over 10,000 calls a year. They’ll walk you through the actual risk level based on the drug, dose, and timing.

Third: Don’t panic. Most birth defects happen for reasons we don’t understand. Medications are just one small piece. Even if a drug is risky, it doesn’t mean your baby will be affected. The odds are still in your favor.

What’s Next? Better Data, Better Care

Right now, 95% of what we know about pregnancy and meds comes from watching what happens after the fact-case reports, registries, and observational studies. We can’t run controlled trials on pregnant women. It’s unethical.

But things are changing. The FDA’s Sentinel Initiative is now tracking 10 million patient records to spot patterns in real time. Researchers are using genetic data to predict who might be more sensitive to certain drugs. Within five years, we may be able to say: “Based on your genes, this drug is likely safe for you.”

Until then, the best tool you have is information-and a trusted medical team. Don’t be afraid to ask questions. Don’t feel guilty for needing help. And never assume a drug is safe just because it’s sold over the counter.

Final Takeaway

You’re not alone in this fear. Nearly 90% of pregnant women take at least one medication. Most of them are fine. A few aren’t. The goal isn’t to avoid all drugs-it’s to make smart, informed choices.

Talk to your doctor before you get pregnant. Keep a list of everything you take. Use reliable sources. And remember: treating your health is part of protecting your baby’s.