A group of scientists says using Tylenol in pregnancy may affect fetal development - but other experts say not to panic

• A group of scientists says acetaminophen - sold as brands including Tylenol - in pregnancy could lead to developmental, reproductive problems.
• It is considered the one safe over-the-counter pain med in pregnancy, used to treat fevers.
• Some experts say the scientists' recommendations don't reveal new data, and may raise unnecessary alarm.

Unlike other over-the-counter pain medications, Tylenol, a popular branded version of acetaminophen, is considered safe in pregnancy for most moms. Medical organizations say it can be used to manage ailments like fever and body aches, and about two-thirds of pregnant people take the drug at some point.

But a global group of 91 medical experts, scientists, and public-health professionals cautioned against using acetaminophen during pregnancy last week, saying it may alter fetal development and is too often used unnecessarily.

In their statement, published in the journal Nature Reviews Endocrinology, they urge pregnant women to avoid acetaminophen if they can, talk to a clinician if they're not sure if their symptoms warrant use, and to use as low a dose for as short a time as possible.

Other experts say the statement isn't different from current guidance - and may be causing undue alarm.

The report says acetaminophen in pregnancy "is something that needs to be looked at, it doesn't actually provide any concerning data," Dr. Stephanie Ros, an OB-GYN and maternal-fetal specialist at the University of South Florida, told Insider. "But I think the overall tone made a lot of people concerned."

Studies have found risks, but some experts say the research is poor quality

In the statement, the scientists say they are "concerned about increasing rates of neurological, urogenital and reproductive disorders." They also note "disturbing increases" in the number of children with cognitive, learning, and behavioral problems, and point to Tylenol as a potential cause.

The drug, they note, has endocrine-disrupting properties, meaning it may interfere with the body's natural hormones that support healthy development. That's why known endocrine disruptors like phthalates, found in everything from cosmetics to plastics, should be minimized during pregnancy.

The authors also point to animal research linking acetaminophen in utero to reproductive disorders and fertility issues in adulthood. Some human studies, too, have found that the drug is associated with an increased risk of undescended testicles and a reduced anogenital distance (which, in turn, is predictive of decreased fertility) in males, and early puberty in females.

The study authors go on to review 29 human studies, 26 of which have found a link between prenatal exposure to Tylenol and development issues like ADHD, autism, and decreased IQ. However, medical organizations have emphasized the limits of such studies.

"The two major governing bodies in the field have analyzed these studies and determined that they were of very poor quality and did not have proper quality controls and did not use good scientific method," Dr. Laura Laursen, an OB-GYN in Chicago, previously told Insider. "Women should not be worried. Tylenol is safe during pregnancy. Hard stop."

In a statement to Insider from Johnson & Johnson, which makes Tylenol, the company said it always recommends using its products as directed. The Tylenol label, it says, states that pregnnat and breastfeeding people should ask a health professional before use.

"We will always evaluate new data," the statement says. "At this time, we are not aware of evidence to support a causal link between acetaminophen use during pregnancy and the risk of adverse fetal outcomes."

'Patients should not be frightened away'

The paper authors call for more thorough epidemiological research on Tylenol in pregnancy. Meantime, they recommend only using Tylenol for fever - which may be linked to birth defects - and skipping it for other issues.

However, Ros told Insider, "tons and tons of exposures" to Tylenol for reasons other than fever, like bodyaches, don't seem to be linked to any increase in developmental issues.

If a pregnant patient does use Tylenol for any reason, the scientists recommend limiting use to two weeks or less, since they say longer durations are more strongly linked to negative outcomes.

Christopher Zahn, vice president of practice activities for the American College of Obstetricians and Gynecologists who was not involved in the paper, told Stat "patients should not be frightened away from the many benefits of acetaminophen" since there's no evidence it directly causes any problems.

"However, as always, any medication taken during pregnancy should be used only as needed, in moderation, and after the pregnant patient has consulted with their doctor," he added.