A new analysis of dozens of peer-reviewed medical studies found no link between the use of Tylenol in pregnancy and diagnoses of autism, ADHD or intellectual disabilities in children.

The research, published Friday in the journal The Lancet, shows that "the best available human evidence does not support a causal link between prenatal Tylenol exposure and autism, ADHD or intellectual disability," said Dr. Céline Gounder, CBS News medical contributor and editor-at-large for public health at KFF Health News. 

"It's as definitive as we're going to get," she said.

The findings support existing recommendations from medical groups like the American College of Obstetricians and Gynecologists on the safety of using acetaminophen, the active ingredient in Tylenol, as the first-line medication for relieving pain or fever during pregnancy, the authors say. 

The researchers reviewed over 40 studies from around the world that used questionnaires or medical records to show outcomes and compared pregnancies with and without Tylenol use. Those studies included large, population-based cohorts from multiple countries, including the U.S., Japan and Australia.

Gounder called the analysis "methodologically strong," especially due to multiple studies that included sibling comparisons to see how outcomes might differ between them even with their shared genetics and environment. 

"When calculating the prevalence of neurodevelopmental outcomes, it is crucial to consider the baseline risk of such conditions within families," the authors wrote. 

Tylenol and pregnancy 

President Trump and Health and Human Services Secretary Robert F. Kennedy Jr. sparked controversy in September when they said they believed Tylenol use in pregnancy may be leading to an increase in autism diagnoses. Kennedy, an outspoken vaccine skeptic, has called autism a "preventable disease." 

Medical experts and health agencies around the world pushed back against those claims, saying evidence shows acetaminophen — known as paracetamol in the U.K. and Europe — is the safest pain reliever option for pregnant women. 

In fact, leaving pain and high fever untreated can be harmful to the mother and fetus, and other pain medications like aspirin and ibuprofen are known to have risks during pregnancy.

Kenvue, the maker of Tylenol, has said, "Independent, sound science clearly shows that taking acetaminophen does not cause autism," calling it "the safest pain reliever option for pregnant women as needed throughout their entire pregnancy." 

A spokesman for the Department of Health and Human Services, Andrew Nixon, responded to the latest study with a statement saying "many experts have expressed concern of the use of acetaminophen during pregnancy, including Dr. Andrea Baccarelli, the Dean of the Harvard School of Public Health." Baccarelli was senior author of a 2025 study that found "evidence consistent with an association between acetaminophen exposure during pregnancy and increased incidence of NDDs" — neurodevelopmental disorders including autism and ADHD.

While some research has suggested there could be a possible association between acetaminophen use and neurodevelopmental disorders, many of those studies looked at relatively small groups and did not prove a link. One such review referenced by Mr. Trump and Kennedy was "limited by data variability and significant differences in how studies defined exposure and outcomes," the authors of The Lancet analysis say. 

Larger and more robust studies, including one in Sweden that followed 2.5 million children for over 25 years, found no connection between the medication and autism. A Japanese study that followed 217,000 children initially appeared to show a slight increased risk, but those findings did not hold up when researchers compared siblings to account for genetic factors. 

The authors of the new research say their findings from the sibling comparisons and their pooled results from multiple studies suggest that previously reported associations between the medication during pregnancy and autism, ADHD or intellectual disabilities may be due to other factors — for example, the mother's underlying pain, fever or genetic predisposition — rather than any direct effect from acetaminophen.