Pregnancy Registries: What We’re Learning About Medication Safety

When a woman finds out she’s pregnant, one of the first questions she asks isn’t about nursery colors or baby names-it’s about the pills she’s been taking. Pregnancy registries are the quiet, behind-the-scenes system trying to answer that question with real data, not guesswork. These aren’t clinical trials. They’re not testing new drugs. They’re watching what happens when women take medications they were already using-antidepressants, seizure meds, autoimmune biologics-and carry a baby to term. The goal? To find out if those drugs might harm the developing baby.

Why Do We Even Need These Registries?

Before a drug hits the market, it’s tested in thousands of people. But pregnant women are almost always left out. Ethical concerns, legal risks, and fear of harming a fetus mean clinical trials skip this group entirely. That leaves doctors and patients flying blind. An estimated 80% of pregnant women in the U.S. take at least one medication during pregnancy. Some are for chronic conditions-epilepsy, diabetes, depression. Others are for short-term issues like infections or nausea. But without data, we don’t know if those drugs are safe.

That’s where pregnancy registries come in. They started gaining traction after the thalidomide disaster in the 1960s, when a drug prescribed for morning sickness caused severe birth defects in thousands of babies. Since then, regulators like the FDA and EMA have required companies to set up registries for certain drugs, especially those likely to be used by women of childbearing age. These aren’t optional. They’re part of the approval process.

How Do Pregnancy Registries Actually Work?

Think of them as long-term watchlists. Women who are pregnant and taking a specific medication can volunteer to join. They’re contacted early in their pregnancy-sometimes even before they know they’re expecting-by a registry coordinator. They answer detailed questions: What drug? When did you start taking it? How much? Are you taking anything else? Do you smoke? Drink? Have diabetes or high blood pressure?

Then, they’re followed throughout the pregnancy. After birth, researchers track whether the baby has any birth defects, was born early, weighed too little, or had other complications. Some registries go further-tracking development at 6 months, 12 months, even into toddlerhood to check for learning delays or behavioral issues. The National Pregnancy Registry for Psychiatric Medications, for example, follows kids up to age one to assess neurodevelopment.

Unlike passive systems that just collect reports of side effects, registries actively recruit participants and collect data in real time. That means less guesswork. No relying on a mother’s memory months later. No missing doses or misremembered dates. This kind of data is gold for researchers.

What Have We Learned So Far?

The data isn’t perfect, but it’s changing practice. For example, registry data helped confirm that certain antiseizure drugs like valproate carry a high risk of neural tube defects and cognitive delays. That’s led to clear warnings: avoid valproate in pregnancy if possible. Other drugs, like some SSRIs used for depression, showed no major increase in birth defects in registry studies-giving anxious moms some reassurance.

For newer biologic drugs used in autoimmune diseases like rheumatoid arthritis or psoriasis, registries have been the only source of safety data. Drugs like adalimumab and certolizumab were once total unknowns in pregnancy. Now, data from registries show they cross the placenta minimally, especially if taken in the third trimester. That’s led to updated guidelines: many women can safely continue these meds during pregnancy.

But here’s the catch: we’re still missing answers for a lot of drugs. There are over 80 active registries in the U.S. alone, covering psychiatric meds, antiepileptics, and biologics. But many drugs-especially older ones or those used for rare conditions-still have no registry at all. And even when registries exist, they’re often too small to catch rare risks.

The Limits: Why Registries Can’t Give You a Guarantee

No registry can say, “This drug is 100% safe.” That’s not how science works. They’re designed to detect big risks-not small ones. Let’s say a birth defect normally happens in 1 out of 100 babies. If a drug doubles that risk to 2%, you’d need over 1,200 exposed pregnancies to spot it with confidence. Most registries enroll far fewer than that. Some have only 50 to 200 women.

Another problem? Who joins? Enrollment is voluntary. Only about 15-20% of eligible women sign up. Those who do are often more anxious, more informed, or more motivated to help science. That means the data might not represent everyone. A woman who skips the registry might be the one who’s less worried, less likely to follow up, or already had a bad outcome. That’s selection bias.

And even when data comes in, it takes years. A registry might run for 3 to 5 years just to collect enough cases. By then, the drug might have been on the market for a decade. That’s why experts say registries are best for spotting signals-not giving final answers.

What’s Changing? The Future of Pregnancy Safety Data

The field is evolving. In 2022, the FDA launched the Pregnancy Safety Research Network to link up multiple registries and standardize how data is collected. That means more power to detect trends. In 2024, the National Pregnancy Registry for Psychiatric Medications added 18 new drugs, bringing its total to 45. That’s progress.

But the real shift is in combining methods. Experts now say registries should be just one piece of the puzzle. They’re paired with large health databases-insurance claims, electronic medical records-that can track tens of thousands of pregnancies. These databases have big numbers but messy data: did the mom actually take the pill? Was the dose right? Registries fix those gaps.

The goal isn’t to replace one system with another. It’s to layer them. Use registries to find a red flag. Then use big data to confirm it. Use big data to find a pattern. Then use a registry to dig deeper.

What It Feels Like to Join a Registry

For the women who sign up, it’s not just science-it’s personal. Many are terrified. They’ve been told their medication might hurt their baby. They’ve been told to stop it, even if it means worsening their own health. Joining a registry gives them a way to take action. They’re not just passive patients. They’re contributors.

MotherToBaby, which runs several registries, found that 78% of women who participated felt they made a difference. They appreciated getting personalized updates, even if the news wasn’t always good. But it’s not easy. Some women drop out. Pregnancy is exhausting. Appointments pile up. Some feel overwhelmed when they can’t get a quick answer. “I just wanted to know if my baby would be okay,” one participant told researchers. “But they said, ‘We’re collecting data. We’ll let you know in a year.’”

Still, many say it’s worth it. They feel less alone. They know their experience helps other women down the line.

Who Runs These Registries? And How Much Do They Cost?

Pharmaceutical companies are required to fund them. A single registry can cost between $500,000 and $2 million a year. That covers staff, outreach, data entry, follow-ups, and reporting to regulators. It’s expensive. That’s why only the most widely used or highest-risk drugs get registries.

Registries are run by academic medical centers, hospitals, or nonprofit groups like MotherToBaby, often in partnership with drug makers. The FDA and EMA oversee them. Every year, sponsors must submit safety reports. Findings are published in medical journals once enough data is collected.

The global market for pregnancy safety monitoring-registries and other tools-is worth nearly $300 million and growing. That’s because regulations are tightening. In the last five years, 65% of new biologics approved by the FDA came with a pregnancy registry requirement.

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

Don’t stop your meds without talking to your doctor. That’s the biggest risk. Untreated depression, uncontrolled seizures, or active autoimmune disease can be far more dangerous to your baby than most medications.

Ask your provider: Is there a registry for this drug? Can I join? Even if you don’t join, ask what the current data says. Many registries have public summaries you can read.

If you’re considering pregnancy, check if your meds are on a registry list. Some websites, like MotherToBaby.org, offer free, evidence-based advice. They’re not a substitute for medical care-but they’re a solid starting point.

Final Thoughts: Registries Are a Lifeline, Not a Crystal Ball

Pregnancy registries don’t give you certainty. But they give you something better: evidence. They turn fear into facts. They turn silence into answers. For women on long-term medications, they’re the only reason we know that some drugs are safer than we thought. For others, they’re the reason we now know to avoid certain ones.

They’re not perfect. They’re slow. They’re small. But without them, we’d be making decisions in the dark. And that’s a risk no pregnant woman should have to take alone.