New review finds Tylenol use in pregnancy not linked to autism

A Lancet review counters autism claims about Tylenol in pregnancy

A new review of studies published in The Lancet Obstetrics, Gynecology & Women’s Health found that taking Tylenol (acetaminophen) during pregnancy does not increase the risk of autism, ADHD or intellectual disabilities. The findings, published Friday, add to other research that has rejected claims promoted by President Donald Trump about a connection between the medication and neurodevelopmental disorders.

The review analyzed 43 studies, and its authors said the most rigorous evidence—such as research designs that compare siblings—offers strong support that taking acetaminophen does not cause autism, ADHD or intellectual disabilities. Lead author Dr. Asma Khalil, a fetal medicine specialist at St. George’s Hospital in London, said acetaminophen is “safe to use in pregnancy.” She added that it “remains … the first line of treatment that we would recommend if the pregnant woman has pain or fever.”

In recent public debate, some studies have suggested the possibility of a link between acetaminophen use in pregnancy and autism risk, and Khalil said those signals are vulnerable to problems that can distort observational findings. She said the association discussed publicly is vulnerable to confounding factors, such as the possibility that a pregnant woman might take Tylenol for fevers and that fever itself could be related to autism risk. Khalil also said the research can be affected by “recall bias,” including situations in which “the mother of an autistic child doesn’t accurately remember how much of the drug she used during pregnancy after the fact.”

Khalil said that when researchers prioritize the more rigorous approaches—particularly sibling comparisons—the association is not seen. “When researchers prioritize the most rigorous study approaches – such as comparing siblings to account for the influence of things like genetics – ‘the association is not seen,’” the AP story reported her saying.

The review comes amid U.S. political dispute over acetaminophen. The AP reported that Trump last year promoted unproven ties between Tylenol and autism and told pregnant women, “Don’t take Tylenol.” The new research was described as continuing a trend of studies finding no clear link, including a review published last year in BMJ and an analysis in JAMA that examined sibling data.

While some evidence cited by the White House has pointed toward a possible association, the AP story described that the BMC Environmental Health paper cited by the administration analyzed results from 46 prior studies and said it supported evidence of an association between Tylenol exposure during pregnancy and increased incidence of neurodevelopmental disorders. The paper’s researchers also wrote that acetaminophen remains important for treating pain and fever during pregnancy, but that steps should be taken to limit use.

Khalil said some of the evidence emphasized in that public debate may be influenced by study limitations. She said the review included some studies that were small and prone to bias. The AP story also noted that the senior author of the BMC Environmental Health work is Dr. Andrea Baccarelli, dean of the faculty at the Harvard T.H. Chan School of Public Health, and that Baccarelli disclosed in the paper that he served as an expert witness for plaintiffs in a case involving potential links between acetaminophen use during pregnancy and neurodevelopmental disorders. The AP reported that Baccarelli did not respond to an email seeking comment.

In a commentary published with the latest Lancet review, researchers who were not involved in the new analysis cautioned that discouraging acetaminophen use during pregnancy could lead to inadequate control of pain or fever. They warned that untreated fever and infection in a pregnant woman poses “well-established risks to fetal survival and neurodevelopment,” according to the AP story, and said that inadequate treatment could harm both the baby and the mother.

The AP story also reiterated that autism risk is driven by multiple factors. It said genetics are the biggest risk factor for autism and listed other risks including the age of the child’s father, preterm birth and whether the mother had health problems during pregnancy.