The review, led by Dr. Asma Khalil of St. George’s Hospital in London, concluded that the most rigorous study designs — including analyses that compare siblings to control for genetic and environmental factors — show no causal link between prenatal acetaminophen use and neurodevelopmental disorders, and that the drug remains safe and appropriate for treating pain and fever during pregnancy.
A review of 43 studies published Friday in The Lancet Obstetrics, Gynecology & Women’s Health found that taking acetaminophen — sold in the United States as Tylenol — during pregnancy does not increase the risk of autism, ADHD or intellectual disabilities, adding to a body of research that contradicts claims promoted by the Trump administration.
President Trump last year told pregnant women “Don’t take Tylenol,” citing what the administration characterized as evidence linking the painkiller to autism. The White House has highlighted a review published in BMC Environmental Health that analyzed 46 prior studies and found support for an association between prenatal Tylenol exposure and neurodevelopmental disorders.
The new Lancet review concluded that the most rigorous studies — particularly those that compare siblings to control for genetic and environmental factors — show no such link.
“It’s safe to use in pregnancy,” said lead author Dr. Asma Khalil, a fetal medicine specialist at St. George’s Hospital in London. “It remains … the first line of treatment that we would recommend if the pregnant woman has pain or fever.”
Methodological concerns
Khalil said the BMC Environmental Health review included studies that were small and prone to bias. Health experts have also noted that only a fraction of the studies in that review focused specifically on autism, and that an observed statistical association does not establish cause and effect.
The senior author of that review, Dr. Andrea Baccarelli, dean of the faculty at Harvard T.H. Chan School of Public Health, disclosed in the paper that he served as an expert witness for plaintiffs in litigation involving potential links between acetaminophen use during pregnancy and neurodevelopmental disorders. Baccarelli did not respond to a request for comment, according to the Associated Press.
Khalil said research showing small associations between acetaminophen and autism is vulnerable to confounding factors. Pregnant women may take Tylenol to treat fever, and fever during pregnancy — not the drug itself — may raise the risk of autism. Studies can also be affected by recall bias, such as when a mother of an autistic child does not accurately remember how much of the drug she used during pregnancy.
When researchers use the most rigorous methods, “the association is not seen,” Khalil said.
Risk of discouraging use
Researchers not involved in the Lancet review, from the London School of Hygiene and Tropical Medicine and Children’s Hospital Colorado, among other institutions, cautioned that discouraging acetaminophen use during pregnancy carries its own risks.
Untreated fever and infection in a pregnant woman poses “well-established risks to fetal survival and neurodevelopment,” they wrote in a commentary published alongside the review.
Broader research context
The Lancet review adds to prior findings. A review published last year in the BMJ found that existing evidence does not clearly link acetaminophen use during pregnancy with autism or ADHD in offspring. A study published the previous year in the Journal of the American Medical Association also found no association with children’s risk of autism, ADHD or intellectual disability in a sibling analysis.
Experts say genetics represent the largest risk factor for autism. Other recognized risk factors include the age of the child’s father, preterm birth and whether the mother experienced health problems during pregnancy.