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This article is republished from The Conversation, an independent and nonprofit source of news, analysis and commentary from academic experts.  is a Distinguished Professor of Pharmaceutical Outcomes & Policy at the . is a Professor of Genetic Medicine at

A panel convened in July 2025 by the Food and Drug Administration sparked controversy by casting doubt about the . But it also raised the broader issue of how little is known about the safety of many medications used in pregnancy, considering the implications for both mother and child – and how understudied this topic is.

In the U.S., the average pregnant patient takes , and more than 9 in 10 patients take at least one. But most drugs lack conclusive evidence about their safety during pregnancy. About uses a medication during pregnancy that has some preliminary evidence that it could cause harm but for which conclusive studies are missing.

We are who evaluate the . In our work, we identify medications that might raise the risk for birth defects or pregnancy loss and compare the safety of different treatments.

While progress has been slow, researchers and federal agencies have built monitoring systems, databases and tools to accelerate our understanding of medication safety. However, these efforts are now at risk due to – and with them, so is the knowledge base for determining whether sticking with a therapy or discontinuing it offers the safest choice for both mother and child.

How pregnant women got sidelined

One big reason why so little is known about the effects of medications during pregnancy stretches back more than half a century. In the 1960s, a that was widely prescribed to treat morning sickness in pregnant women caused severe birth defects in over 10,000 children around the world. In response, in 1977 the FDA recommended from participating in early stage clinical trials testing new medications.

Thalidomide, sold under several brand names including Kevadon, was used in many countries to treat morning sickness, though the Food and Drug Administration never approved it for that purpose in the United States. Ethically, there is long-standing tension between concerns about fetal harm and maternal needs. Legal liability and added complexities when conducting studies in pregnant women serve as .

When drugs are approved, studies about whether they might cause birth defects are , and they often don’t translate well to humans. So when a new medication comes on the market, nothing is known about how it affects people during pregnancy. Even if animal studies or the medication’s mode of action raised concerns, the drug can still be approved, though companies observing its effects when taken during pregnancy.

Cause and effect

Of 290 drugs approved by the FDA between 2010 and 2019, on the risks or benefits for pregnant patients. About 80% of some 1,800 medications in a , which summarizes evidence on medications’ risks during pregnancy, lack or have limited evidence about the risks for birth defects. Researchers to pin down whether a medication is safe to use in pregnancy.

As a result, many pregnant women stop treating their chronic diseases. In a U.S. study published in 2023, over one-third of women , and 36.5% of those did so without advice from a health care provider. More than half cited concerns about birth or developmental defects as the reason.

Yet uncontrolled chronic disease comes with its own toll on both the mother’s and the baby’s health. For example, some medications used to treat seizures are known to cause birth defects, but stopping them may increase seizures, which themselves .

Women with severe or recurrent depression who abruptly stop their antidepressants , which is in turn associated with increased risk of substance use, inadequate prenatal care and other negative effects on fetal development. Stopping the use of medications for treating high blood pressure – specifically, a greater risk of pregnancy-related high blood pressure that can cause organ damage, called ; a condition called , when the placenta detaches from the wall of the uterus too early; preterm birth; and fetal growth restriction. An online resource called , created by a network of experts on birth defects, provides an excellent summary of the available data on medication safety during pregnancy.

The FDA in some cases requires drug companies to establish registries to track the outcomes of pregnancies exposed to certain medications. These registries can be useful, but they . For example, recruiting pregnant patients into them takes time and considerable effort, resulting in small sample sizes that may not capture rare birth defects. Also, registries typically follow a single medication and rarely include comparisons to alternative treatment approaches – or to no treatment.

What’s more, following the overturning the constitutional right to abortion, to add their names to a pregnancy registry or to provide data on prenatal detection of birth defects due to concerns about privacy and legal risks.

Decades of underfunding

In 2019, a established by the identified a major gap in knowledge about drug safety and effectiveness in pregnant and lactating women and to fill it.

However, little has changed. A 2025 review by the National Academies of Sciences, Engineering and Medicine pointed out that research funding for women’s health topics , while the overall budget of the National Institutes of Health has steadily increased. The review recommended doubling the NIH funding allocated for such research, but this seems unlikely in light of the recent proposals to .

The National Institute of Child Health and Human Development funds the across federal agencies, although the institute has an than most of its sister institutes such as the National Cancer Institute. Grants awarded are typically broad and take four to five years to complete, but they allow the more comprehensive assessments that are needed to support informed decisions considering outcomes for mother and child. For example, NIH-funded researchers have established a clear link between , a potent teratogen used to treat epilepsy and several mental health disorders.

The Centers for Disease Control and Prevention as well as the FDA have also funded specific pregnancy-related research. For example, following the COVID-19 epidemic, for studies that help expedite pregnancy safety studies for treatments that might be used for newly emerging infections. In response to emerging concerns about a substance called gadolinium, which is often used during MRI procedures, the FDA funded our own work on , which .

For healthy pregnancies, more research is critical

These efforts have laid a crucial foundation for evaluating medication safety and effectiveness during pregnancy. But keeping pace with the release of new medications and new ways they are used, as well as addressing the backlog of missing evidence for medications that were approved in the past millennium, remain a challenge.

Recent have focused on topics presumably relating to diversity, equity and inclusion. But research on – for example, on the – has been affected as well.

The NIH has scaled back new grant awards since the beginning of 2025, and the . Proposed sweeping leave their role in supporting research on healthy pregnancies similarly uncertain.

In our view, removing or reducing ongoing investments in healthy pregnancies poses a danger to much-needed efforts to reduce as well as and deaths.

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