September 23, 2025
Francis Chung/Sipa USA
Health and Human Services Secretary Robert F. Kennedy Jr. and President Donald Trump claim that using Tylenol while pregnant may cause autism. Scientists say research is inconclusive.
President Donald Trump and his top health officials on Monday declared, without presenting definitive scientific evidence to support the claim, that pregnant women who take acetaminophen increase the risk of their children developing autism spectrum disorder.
Research into a possible link between neurological conditions like autism and the use of acetaminophen, the active ingredient in Tylenol, during pregnancy have produced conflicting results. Some studies, including one published by BMC Environmental Health in August, have suggested a link, but others have not.
The Food and Drug Administration moved to update labels on acetaminophen products so they note evidence suggests that using them during pregnancy may increase the risk of autism. But the FDA also noted that a causal relationship has not been established.
The FDA also issued a letter warning physicians of the risk of using acetaminophen during pregnancy, and approved the use of an existing drug as a treatment for autism symptoms.
During Monday's announcement, Health and Human Services Secretary Robert F. Kennedy Jr. cited the most recent study on acetaminophen, which evaluated previous research and concluded that pregnant women should "limit acetaminophen consumption to protect their offspring's neurodevelopment."
But many scientists, including David Mandell, a professor of psychiatry at the University of Pennsylvania and director of the Penn Center for Mental Health, pushed back against assertions made by federal officials.
Mandell said some studies have suggested an association between developmental delays and acetaminophen use, but the medical causes that prompt pregnant women to take Tylenol may play more of a factor. He pointed to the conclusions of a study published in April 2024 in the Journal of American Medical Association.
"Women who have children with neuro-developmental delays report more headaches and pain during pregnancy than other mothers," Mandell said. "We also know that fevers in pregnancy, in the second and third trimester especially, can increase risk for having a child with neuro-developmental delay. ... When you take that into account, there's no association between acetaminophen and autism."
Kenvue, the New Jersey company that makes Tylenol, believes "sound science clearly shows that taking acetaminophen does not cause autism," spokesperson Melissa Witt told the New York Times. "We strongly disagree with any suggestion otherwise and are deeply concerned with the health risk this poses for expecting mothers and parents."
Mandell also said the messaging by Trump, who called Tylenol "very dangerous" and urged pregnant people never to take it, could lead to expectant mothers experiencing significant pain, and potentially place themselves and their babies at risk of other health issues.
Autism is a complex neuro-developmental disorder that manifests in different ways, including limited and repetitive behaviors and problems with social communication and interaction. Scientists believe it is caused by various factors, including genetics and environmental factors.
Trump and Kennedy also repeated false claims about vaccines during their remarks Monday, including a disproven claim that vaccines cause autism. Their remarks brought sharp rebukes from scientists.
Dr. Paul Offit, director of the Children's Hospital of Philadelphia's Vaccine Education Center, called the press conference "dangerously irresponsible."
"Here you have the president of the United States and his bully pulpit, you have the secretary of Health and Human Services and his bully pulpit, both telling you that vaccines are basically causing chronic disorders," Offit told the Washington Post.
Arthur Caplan, head of New York University's Grossman School of Medicine's Division of Medical Ethics. said that regurgitating these talking points poses a real threat to maternal and prenatal health.
"The announcement on autism was the saddest display of a lack of evidence, rumors, recycling old myths, lousy advice, outright lies and dangerous advice I have ever witnessed by anyone in authority in the world claiming to know anything about science," Caplan said in statement. "What was said was not only unsupported and wrong but flat out malpractice in managing pregnancy and protecting fetal life."
Autism diagnoses have increased by nearly five-fold over the past 20 years, according to a CDC report released in April. On Monday, Trump called the rise in autism cases one of the most "alarming public health developments in history."
Mandell said the sharp increase likely is a result of significant changes to the diagnostic process in that period.
"We have changed dramatically what we call autism," he said. "We started creating a service system and treatments and supports for autistic kids that didn't exist before. ... There's a lot more value to the diagnosis than there used to be. I think physicians are much more willing to give it, because they know it's going to lead to the child getting services that they might not otherwise get."
Federal officials also touted leucovorin — folinic acid, a modified version of vitamin B9 — as a potential treatment for autism. The drug currently is used to treat anemia and counteract the side effects of chemotherapy and anti-bacterial medications. Vitamin B9, also known as folate, is believed to lower the risk of birth defects in a baby's brain or spine.
The FDA is moving to approve the drug as a treatment for people with cerebral folate deficiency, because they have been found to have development delays consistent with autism. The FDA cited research from 2009 to 2024 that "supports a finding" that leucovorin can help people with cerebral folate deficiencies.
"Children are suffering and deserve access to potential treatments that have shown promise," FDA Commissioner Dr. Marty Makary said in a statement. "We are using gold standard science and common sense to deliver for the American people."
Mandell called the FDA's decision on leucovorin short-sighted, adding that he has concerns about the sample size and statistical approaches used in the studies cited by the federal government and the consequences the decision could have on families.
"There are going to be people who set up shop selling vitamin B9 or folinic acid and desperate families are going to pay a lot of money to get it without evidence that it helps their child," Mandell said.
