Carbamazepine and the Risk of Birth Defects: What Pregnant Women Need to Know

If you’re taking carbamazepine and just found out you’re pregnant, you’re not alone-and you’re not panic-stricken for no reason. Thousands of women worldwide take this medication for epilepsy, bipolar disorder, or nerve pain, and many of them get pregnant without knowing the risks. The truth isn’t black and white. Carbamazepine isn’t a poison. But it’s not risk-free either. Understanding the real numbers, the real studies, and the real alternatives can help you make a calm, informed choice.

What Is Carbamazepine?

Carbamazepine is an anticonvulsant and mood-stabilizing drug first approved in the 1960s. Also known as Tegretol, it works by calming overactive nerve signals in the brain. It’s prescribed for epilepsy, trigeminal neuralgia, and sometimes bipolar disorder when other medications don’t work.

It’s not a new drug. It’s been used for over 60 years. That means doctors have a lot of data on how it behaves in the body-and in pregnant bodies. But data doesn’t always mean safety. In fact, carbamazepine has one of the clearest links among antiseizure medications to certain birth defects.

What Birth Defects Are Linked to Carbamazepine?

Studies show that babies exposed to carbamazepine in the first trimester have a slightly higher chance of developing major physical abnormalities. The most common include:

• Neural tube defects, like spina bifida
• Cleft lip or palate
• Heart defects
• Low birth weight
• Developmental delays

The absolute risk isn’t huge. For example, the general population has about a 1-2% chance of a major birth defect. With carbamazepine, that number rises to around 4-6%. That’s a doubling of risk-but it still means 94-96 out of 100 babies are born without major issues.

What’s more concerning is the pattern. Babies exposed to carbamazepine in early pregnancy can develop what’s called Fetal Anticonvulsant Syndrome (FACS). This isn’t a single defect but a group of subtle facial features and developmental delays that show up over time: wide-set eyes, flattened nasal bridge, small head size, and sometimes learning or behavioral challenges later in childhood.

Why Does This Happen?

Carbamazepine crosses the placenta easily. That means your baby’s developing organs are exposed to the same drug levels as yours. The drug interferes with how folate-vitamin B9-is used in the body. Folate is critical in the first 28 days after conception, when the neural tube (which becomes the brain and spine) is forming.

Unlike some other antiseizure drugs, carbamazepine doesn’t just lower folate levels-it also breaks down folate faster. That’s why doctors often recommend high-dose folic acid (at least 5 mg per day) before and during early pregnancy for women on carbamazepine. It doesn’t eliminate the risk, but it cuts it significantly.

There’s also evidence that carbamazepine activates certain enzymes in the liver that can alter how other essential nutrients are metabolized. This isn’t just about folate-it’s about a cascade of small disruptions during a time when every cell division matters.

How Does It Compare to Other Antiseizure Drugs?

Not all epilepsy medications carry the same risk. Here’s how carbamazepine stacks up against others commonly used during pregnancy:

Lamotrigine and levetiracetam are now often first choices for women with epilepsy who are planning pregnancy. They’re just as effective for seizure control, but their safety profile is much better. Carbamazepine still has a role-but only when other drugs don’t work or cause side effects.

What Should You Do If You’re on Carbamazepine and Pregnant?

Do not stop taking carbamazepine on your own. Seizures during pregnancy can be more dangerous than the medication. A single grand mal seizure can cause oxygen loss to the baby, premature labor, or even miscarriage.

Instead, here’s what to do:

1. Call your neurologist or OB-GYN immediately. Don’t wait for your next appointment.
2. Start high-dose folic acid (5 mg daily) if you haven’t already. Take it until at least week 12 of pregnancy.
3. Ask about switching to lamotrigine or levetiracetam. Many women make the switch safely in the first trimester.
4. Get an early anatomy scan (18-22 weeks) to check for structural abnormalities.
5. Consider a fetal echocardiogram to screen for heart defects.

If switching isn’t possible-for example, if you’ve tried other drugs and they didn’t work-your doctor may lower your dose slightly or split it into smaller doses throughout the day to reduce peak blood levels. Blood tests during pregnancy are key: carbamazepine levels drop as pregnancy progresses, so your dose may need adjusting to keep seizures controlled without overmedicating.

What If You’re Planning Pregnancy?

Planning ahead changes everything. If you’re on carbamazepine and thinking about having a baby:

• Start folic acid at least 3 months before trying to conceive.
• Have a preconception counseling session with your neurologist and OB-GYN.
• Ask if you can switch to a safer drug before pregnancy begins.
• Track your menstrual cycle and avoid unplanned pregnancy.
• Make sure your seizure control is stable before conception. Uncontrolled epilepsy is the biggest risk to your baby.

Some women stay on carbamazepine through pregnancy because their seizures are so severe or unpredictable. That’s a valid choice-but only after you’ve fully weighed the risks and benefits with your care team.

What About Breastfeeding?

Carbamazepine passes into breast milk, but in very small amounts. Most babies tolerate it fine. Studies show no major developmental delays in breastfed infants exposed to carbamazepine. The American Academy of Pediatrics considers it compatible with breastfeeding.

Watch for signs your baby might be affected: excessive sleepiness, poor feeding, or unusual fussiness. If you notice any of these, talk to your pediatrician. But don’t stop breastfeeding without medical advice. The benefits of breast milk usually outweigh the tiny drug exposure.

Real Stories, Real Choices

One woman in Sydney, 32, took carbamazepine for 10 years for epilepsy. She got pregnant unexpectedly. Her neurologist switched her to lamotrigine in week 6. She had a healthy baby boy at 38 weeks. No birth defects. No seizures during pregnancy.

Another woman, 29, had bipolar disorder and was on carbamazepine. She didn’t want to switch meds because she’d tried everything else. She took 5 mg folic acid daily and had a detailed scan at 20 weeks. The scan showed a mild cleft lip, which was repaired after birth. Her daughter is now 4, speaks clearly, and is in kindergarten.

These aren’t rare cases. They’re common outcomes when women are informed, supported, and monitored closely.

What’s the Bottom Line?

Carbamazepine does carry a risk of birth defects. But that risk is manageable. It’s not a reason to avoid pregnancy. It’s a reason to plan carefully, act early, and work with your doctors.

Most women who take carbamazepine during pregnancy have healthy babies. The key is not fear-it’s preparation. Know your options. Get the right supplements. Monitor your levels. Choose the safest drug possible. And never, ever stop your medication without talking to your doctor.

Frequently Asked Questions

Next Steps

If you’re currently taking carbamazepine and thinking about pregnancy-or already pregnant-your next move is simple: book a consultation with your neurologist and OB-GYN. Bring your current prescription, your last blood test results, and a list of questions. Don’t wait. The earlier you plan, the better your chances of a healthy pregnancy.

If you’re not pregnant but want to be, start folic acid now. Talk about switching medications. Get your seizures under control. This isn’t about fear. It’s about control. And with the right support, you can have the family you want-safely.