Fights over Tylenol, SSRIs highlight the enduring lack of pregnant women in drug trials

STAT News – Thursday, October 2, 2025
By Lizzy Lawrence

Researchers have shut pregnant women out of gold-standard clinical trials in order to protect them and their babies. But the practice has had the opposite effect.

Instead, women have to wade through a chaotic data landscape, and many may choose to suffer through untreated illnesses.

Besides sowing confusion, the lack of data makes it easier for people to obfuscate and misconstrue existing data. That dynamic was on full display last week as President Trump and Health and Human Services Secretary Robert F. Kennedy Jr. urged pregnant women to avoid Tylenol as they claimed, without clear evidence, that the active ingredient acetaminophen causes autism.

The existence of this data gap is well established. But it’s gained new relevance as federal officials zero in on the medical decisions of pregnant women, searching for evidence of harm to fetuses.

In July, the Food and Drug Administration put together a panel filled with antidepressant skeptics who said, without compelling data, that SSRIs were likely to harm developing babies. In May, Kennedy unilaterally pulled a recommendation that healthy pregnant women receive Covid vaccines, diverging with medical experts who urge vaccination to protect against illness and to spread immunity to the infant.

With the exception of Trump telling women to “tough it out” rather than take Tylenol, the administration has mostly shied away from offering pregnant women explicit advice. But introducing skepticism in the absence of clear data could be dangerous, experts say, leaving women vulnerable to high fevers and untreated depression.

It’s not clear whether the administration will accompany these initiatives with a full-throated effort to invest in research for pregnant women.

“While HHS cannot comment on pending or future policy decisions, the Department remains firmly committed to applying gold-standard science to deliver real results for pregnant women and families across America,” said HHS spokesperson Emily Hilliard.

The randomized controlled trial isn’t the only way to measure a drug’s safety and efficacy. Pregnant women have benefitted from large studies looking at a medication’s effects over time. SSRIs, acetaminophen, and the Covid vaccine — the pharmaceuticals that have come under HHS scrutiny — are actually among the ones that have been studied the most.

Obstetricians, research ethicists, and birth defect experts told STAT that the government should fund more well-controlled medical trials for pregnant women, along with high-quality observational research to look at medications that have already been approved.

“If they want a healthy population, invest in studies that clarify the safety and efficacy of medications in pregnancy, because they will be used and they are needed,” said Anne Drapkin Lyerly, a bioethicist and obstetrician at the University of North Carolina at Chapel Hill.

Why pregnant women were excluded from drug trials

Before the late 1950s, people generally assumed the placenta was a firm barrier protecting the fetus from exposure to drugs taken by the mother. Then came thalidomide, a drug offered to pregnant women between the late 1950s and early 1960s as a treatment for morning sickness. The medication led to severe limb deformities in more than 10,000 babies.

The crisis, mostly avoided in the United States because of a single reviewer’s refusal to approve the drug, led to the creation of modern drug regulation standards. In 1962, Congress passed a law requiring drug makers prove their products were safe and effective through adequately controlled clinical trials.

The crisis also made doctors more wary of prescribing pregnant women any medication. When drugmakers started enrolling people in randomized trials, they excluded pregnant women.

“Instead of studying pregnant women more, they closed the door on that research, which is really paradoxical when you think about it,” Lyerly said. “But at the time, it seemed like the responsible thing to do.”

The restrictions encompassed all women of childbearing age for years. After decades of advocacy by women’s groups and others, Congress in 1993 passed a law requiring researchers to include women and people of color in all clinical trials. But enrolling pregnant women was still rare.

To tackle this problem, the government established a task force on research specific to pregnant and lactating women as part of the 21st Century Cures Act passage in 2016. One obstacle was the government’s designation of pregnant women as a vulnerable population that required extra protections in clinical research, despite pregnancy not having any impact on a person’s ability to provide informed consent.

“We don’t want to protect women from research, we want to protect women with research,” said Sonja Rasmussen, a Johns Hopkins pediatrician and clinical geneticist who participated in the task force discussions. “The important thing was, rather than assuming exclusion, assume inclusion.”

The government removed that designation in 2018. But cultural and logistical obstacles remain, mostly having to do with effort, money, and fear. Drugmakers might worry about legal liability, or balk at the added costs of making trials safe for pregnant women.

The FDA recommends that companies run developmental and reproductive studies in pregnant animals before testing products in people. Companies may need to hire people with specific expertise in obstetrics.

“It’s actually very hard to do research in pregnant women, largely coming from a good place of wanting to ensure that there are adequate safety standards and adequate preclinical research. But it can make that research slower and more expensive,” said Alyssa Bilinski, a health policy professor at Brown.

Time and money were the reasons Moderna and Pfizer did not include pregnant women in their initial Covid vaccine trials. The FDA asked manufacturers to run developmental and reproductive toxicity studies. Pfizer’s and Moderna’s spokespeople each told STAT the companies wanted to move the trials along as quickly and safely as possible during the Operation Warp Speed sprint.

“Given the unique considerations for the evaluation of the safety and efficacy of medicinal products, including vaccines, in pregnant women, early trials prioritized the study of safety and efficacy of Spikevax in non-pregnant adults,” said Moderna spokesperson Christopher Ridley.

Pfizer did launch a randomized controlled trial in healthy pregnant women in late 2021. But U.S. and other health authorities officially recommended the vaccine for pregnant women in September, making the vaccine easily accessible and sinking the number of people enrolling in Pfizer’s trial.

“With the declining enrollment, the study had insufficient sample size to assess the primary immunogenicity objective,” Pfizer wrote at the time.

Though there’s observational data and a national registry pointing to the vaccine’s safety during pregnancy, some experts consider the exclusion of pregnant women from the key clinical trials a missed opportunity. That would have offered the best data for a population particularly at risk for severe Covid-19.

“It would have been appropriate and preferable to include pregnant women in earlier trials of the Covid vaccine,” Lyerly said. “But they were not involved. So the gaps in collecting data opened the floodgates for fear and misinformation.”

How to make enrolling pregnant women the standard

Rasmussen said that when she’s able to tie a child’s birth defect to a particular gene, the family is often grateful. The mothers have spent years wracked with guilt, convinced that some choice they made during pregnancy was to blame. Spreading unfounded claims about Tylenol or SSRIs compounds that guilt, she said.

Dawn Troost, an attorney in Illinois, went off her antidepressant while trying to conceive, and the result was disastrous; she started taking it again and now has a healthy toddler. She is concerned that the FDA’s panel on SSRIs and the White House’s press conference on acetaminophen spread needless fear.

“When mothers hear that they could harm their child, they may not be getting the best care for themselves, and in turn, do exactly what they so desperately do not want to do, which is hurt their fetus,” Troost said.

Maternal health experts hope the administration’s focus on potentially harmful exposures during pregnancy will translate to a push for more well-designed research, so that scientists don’t have to rely on confusing safety signals. The federal task force put together a long list of recommendations, should the government make expanding clinical research during pregnancy a priority.

The group suggested the National Institutes of Health invest in studies that clarify the safety and efficacy of medications during pregnancy, and adjust grant times to allow for slower enrollment. Another suggestion was to ensure trial investigators are familiar with common issues during pregnancy, so they’re able to tell if miscarriage rates are outside a normal range, for example.

Liz O’Brien, senior director of global drug development at clinical research organization ICON, said boosting trust among pregnant women is key. She suggested researchers gather community input, allow for remote enrollment, and clearly communicate the specific risks and benefits for pregnant individuals.

“In order to safely enroll pregnant women, companies and trialists need to clearly explain safety guidance and remove barriers of misconceptions with transparency and education,” O’Brien told STAT. “This can help encourage those who may be less sure of participation.”

Meanwhile, the government is at least trying to clarify requirements for industry. In July, the FDA released a draft guidance on the appropriate inclusion of pregnant and lactating women in clinical trials.

Pregnant women have been included in trials before; for example, during trials for the RSV vaccine, which is administered during pregnancy in order to protect newborns from the illness. The goal is to identify the best treatments for moms, and stamp out misinformation, by enrolling them in trials focused on their own health, too.

“We’ve felt really positive about this changing in the past, and it hasn’t,” said Rasmussen, the Johns Hopkins pediatrician. “It isn’t right for pregnant women not to know whether something’s safe or not, and to be left feeling guilty.”

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