Six months after President Donald Trump shocked mainstream medicine by saying pregnant women shouldn’t take Tylenol because it is “associated with a very increased risk of autism,” the effects of his comments are still rippling across the country.
Early analysis of hospital prescriptions since September suggests fewer pregnant patients in emergency rooms were taking acetaminophen, the generic name for the drug Tylenol, in the first few months since the White House announcement, according to a recently published report in the medical journal, The Lancet.
A state attorney general has sued Tylenol’s makers, arguing they did not disclose the risks. And amid concerns about autism misinformation, researchers have founded an independent group to rival government efforts.
Even a scientist who has prominently argued that there is a link between Tylenol and autism thinks Trump oversold the risk to pregnant women.
Dr. William Parker, a biochemist with ties to Health and Human Services Secretary Robert F. Kennedy Jr., has argued for years that acetaminophen is linked to autism — claims that have formed the basis of the Trump administration’s anti-Tylenol stance.
But in a recent interview with CNN, Parker admitted the alleged link between acetaminophen use in pregnancy and autism is supported by only the “weakest data.”
Instead, Parker says the risk is more associated with giving it to newborns, a link that mainstream research does not support. In fact, researchers whose work Parker has based his conclusions on say that he’s misinterpreting their results. Parker says they’re the ones misinterpreting the data.
‘Significant repercussions’
The debate over Tylenol’s safety has spilled into courtrooms and conference halls.
In October, Texas Republican Attorney General Ken Paxton sued Tylenol maker Kenvue and Johnson & Johnson, which originally developed the drug, for “deceptively marketing Tylenol to pregnant mothers.”
Paxton alleges the companies knew that early exposure to acetaminophen, Tylenol’s only active ingredient, leads to a “significantly increased risk of autism and other disorders.”
In February, a Texas judge rejected Kenvue’s request to dismiss the case.
Kenvue has said “independent, sound science” has shown acetaminophen does not cause autism. Major medical associations including the American College of Obstetricians and Gynecologists have also pushed back on such claims and said acetaminophen is the safest pain reliever to use during pregnancy.
President Donald Trump, alongside Health and Human Services Secretary Robert F. Kennedy Jr., answers questions on September 22, 2025, after federal health officials suggested a link between the use of acetaminophen during pregnancy and autism. Andrew Harnik/Getty Images
“The dissemination of false information [has had] significant repercussions,” Dr. Helen Tager-Flusberg, a professor emerita at Boston University and director of the Center for Autism Research Excellence, said in March at an event convened by autism researchers.
In an effort to take back the narrative and organize against what they see as a movement based on misinformation, Tager-Flusberg and other autism experts founded an independent group in January to coordinate research and counter the administration’s shifted focus.
“All of this has very a significant impact on science,” Tager-Flusberg said during the group’s first meeting.
From researcher to influencer
Parker, meanwhile, still agrees with the Trump administration’s overall push to link Tylenol to autism — even if he differed with the president’s statement on use by pregnant women.
A biochemist and immunologist, Parker acknowledges that he is a scientist, not a doctor. He doesn’t work with patients or make diagnoses.
As a researcher at Duke University, Parker said he started looking into acetaminophen and autism nearly two decades ago after work on the digestive tract and autoimmune disorders.
He and his co-authors published their “first real good” paper, as he put it to CNN, on the purported link in 2017, writing that acetaminophen could be “one explanation for the increased prevalence of autism.”
But his work didn’t pick up much traction then.
Parker left Duke in 2021 and started his own lab, WPLab, studying links between the immune system and acetaminophen.
When Kennedy announced last spring that he would have answers about autism’s causes in six months, Parker’s theories quickly moved into focus.
While Parker declined to comment about his contact with Kennedy and the Trump administration, he previously told The Atlantic that he spoke with the health secretary, and other health officials including National Institutes of Health Director Jay Bhattacharya, last summer about his research.
And he’s been welcomed by Kennedy’s inner circle. Parker appeared in March on the weekly MAHA Action call led by Tony Lyons, a Kennedy campaign fundraiser and president of Skyhorse Publishing, which will release Parker’s book, “Tylenol and Autism,” in June.
“Acetaminophen causes many, if not most, cases of autism spectrum disorder,” he told listeners.
To Parker, the connection is so clear that there is no need for more research on acetaminophen, at least.
But the focus on use during pregnancy has left him befuddled and a little frustrated.
“Why is everyone focused on one line of evidence?” Parker told CNN. “It’s nothing like the risk of using acetaminophen, say, during labor and delivery or during the first two months of life, or even the first three years of life.”
Autism researchers are also frustrated — by Parker’s continued efforts to link Tylenol use to autism.
Parker has relied in part on data from Sweden, published by the Karolinska Institutet and Drexel University, whose scientists dispute his interpretation of their work.
“If we come up with these things that are just associations and we start to intervene on them, the kind of the best-case scenario is that we’ve wasted our time and money,” said Dr. Renee Gardner, a toxicologist at Karolinska Institutet who led an oft-cited study that says there is no link between acetaminophen use and autism. “But the worst-case scenario is that we actually do potential damage.”
Acetaminophen is advised by major medical organizations as the only safe pain and fever reliever during pregnancy.
The federal shift in focus
The administration’s views on autism have resulted in a big shift in federal funding, leading to an infusion of money into research on the causes of autism, but cuts across federal scientific research overall.
NIH’s $50 million initiative to study the causes of autism, announced last year, will fund projects such as research on genetic factors to environmental exposures and on diet.
More recently, Kennedy dismissed an entire panel of autism experts advising government research, the Interagency Autism Coordinating Committee, and appointed a new committee that included people who have supported the disproven theory that vaccines cause autism. At least one of the newly appointed members, Dr. Elizabeth Mumper, has backed the link between acetaminophen and autism, telling a Texas news station in September that “I became aware of this problem about two decades ago.”
Food and Drug Administration Commissioner Dr. Marty Makary stands in front of a board displaying medical articles during the September 22 announcement from Trump. Kevin Lamarque/Reuters
Researchers and advocates, including former members Kennedy dismissed from the IACC, have lamented the narrow focus this administration has taken.
Several of them, including Tager-Flusberg, this January formed the Independent Autism Coordinating Committee — a pointed reference to the reassembled government panel.
Meeting in March around a long table in a wood-paneled room of the National Press Club, members of the new, nongovernmental group discussed the impact they were already seeing.
Overall funding for autism research has increased, but with scientists left in limbo by federal spending cuts, nongovernmental organizations are stepping in to fund studies, said Alison Singer, founder of the Autism Science Foundation.
Private funding for autism-related studies surged from 17.5% of total funding in 2020 to 40% of an estimated $560 million last year, she said during the meeting.
The inaugural meeting, which spanned most of the day, included some presentations on genetic drivers of autism but largely dwelled on other research and policy the members said is badly needed: access to care, costs, quality of treatments and of life for people with autism.
Their reconstituted government counterpart, now stocked with Kennedy appointees, has not yet met this year.
