President Donald Trump announced the results of his top health advisers’ search for the cause of autism Monday: Tylenol, or acetaminophen, in pregnancy.

Toxicology studies, epidemiology studies and laboratory animal studies have accumulated since at least 2016 showing a plausible link between prenatal and early infancy exposure to Tylenol and neurodevelopmental disorders.

Trump was flanked by his Health and Human Services Secretary Robert F. Kennedy Jr., Centers for Medicare and Medicaid Services Administrator Mehmet Oz and National Institutes of Health Director Jay Bhattacharya.

“Taking Tylenol is not good. For this reason they are strongly recommending women limit Tylenol use when pregnant unless medically necessary,” Trump said.

Trump said he wants to see urgent work from his cabinet to address the steep rise in autism.

“It used to be 1/20,000, then in 1/10,000, I would say that was probably 18 years ago,” Trump said at the White House. “Now it’s 1/31. For boys it’s 1/12.”

Trump recommended only taking it “if you can’t tough it out” with a high fever.

FDA will issue a physician’s notice about the risk of acetaminophen and initiate a change to the drug label. HHS will launch a public service campaign to inform families. FDA will conduct more studies. NIH will launch 13 new projects totaling $50 million into both environmental and genetic causes.

Kennedy also said that folate deficiency can drive autism. FDA will initiate a label change to enable the use of a drug called leucovorin to treat this deficiency.

Drugmaker Kenvue did not respond to a request for comment.

Trump also recommended some changes to vaccines such as removing additives like mercury and aluminum and recommending children take the measles, mumps and rubella (MMR) and varicella vaccines separately. That follows a recommendation by a Centers for Disease Control and Prevention (CDC) vaccine panel to change the vaccine schedule to recommend two separate shots for children under four. Trump also recommended delaying vaccination against Hepatitis B from the day of birth to 12 years of age. The CDC vaccine panel delayed a vote to change the Hep B vaccine recommendation last week.

Kennedy and Bhattacharya said no potential driver would be too taboo, including vaccines.

While some scientists express confidence in their conclusion that an association exists, other studies have resulted in more ambiguous results or have pointed away from an environmental cause toward a genetic one.

The announcement bucks conventional thinking on autism: That its root cause lies in unchangeable genetics. The link may have gone undetected because acetaminophen — first synthesized in the 1890s and grandfathered in by the Food and Drug Administration without clinical trials before modern drug regulation laws — is so widely used and viewed as safe, one expert advising the administration told the Daily Caller News Foundation.

“We know that smoking causes lung cancer. Imagine if everyone in the United States, even babies, smoked cigarettes. Lung cancer would look genetic,” said the expert, who spoke to the DCNF earlier this month and requested anonymity in order to speak candidly about the ongoing study.

While some scientists express confidence in their conclusion that an association exists, other studies have resulted in more ambiguous results or have pointed away from an environmental cause toward a genetic one.

About 50% of pregnant women take acetaminophen, a 2025 study found.

As early as 2016, a Danish national birth cohort study found that acetaminophen was associated with autism spectrum disorder with hyperactive symptoms. More recently, an August 2025 study found that a literature review supported an association between acetaminophen exposure during pregnancy and increased incidence of neurodevelopmental disorders like autism.

But a 2024 study in the premier journal JAMA compared children exposed to acetaminophen during pregnancy with siblings who weren’t and found no association — pointing toward genetic drivers.

Johnson & Johnson spun off the consumer products division that sold Tylenol into a fully independent company called Kenvue in 2023 and sold its remaining stake in the new company 2024. Kenvue is now litigating an appeal in a class action lawsuit that consolidated 600 lawsuits on behalf of 250,000 plaintiffs over Tylenol use in pregnancy.

In 2023, U.S. District Court Judge Denise Cote granted summary judgement for Kenvue after tossing the testimony of five expert witnesses from the opposing side, citing the case’s “great public health implications,” according to the New York Law Journal. The firm is appealing and challenging that move as an overstep of her authority, while Kenvue and sellers of generic acetaminophen like Walmart and CVS have asked that the judge’s order be upheld. Oral arguments in the appeal begin Oct. 9.

“Only 7% of women take acetaminophen in pregnancy to treat a fever while 93% of uses are for aches and headaches,” said Ashley Keller, lead counsel with Keller Postman, the first law firm to file tort cases on this theory in 2022, in an interview with the Daily Caller News Foundation. “This is no judgement of moms. Moms are taking this with reckless abandon because they haven’t been informed of the risks.”

The rise in autism may relate to Tylenol’s relatively newfound status as the only “safe” pain reliever and fever reducer for pregnant women, according to Keller. FDA warned pregnant women not to use aspirin during the last three months of pregnancy in 1990. Ibuprofen, which became over-the-counter in 1984, has long been discouraged in late pregnancy.

Paradoxically, acetaminophen is linked to more deaths than any other over-the-counter pain reliever by far, according to overdose data reported in a 2013 ProPublica investigation. Prescription drugs containing acetaminophen have a black box warning warning that overdosing can lead to liver transplant and death, but over-the-counter Tylenol doesn’t. Plaintiffs in the case against Kenvue are seeking a label change.

McNeil Consumer Healthcare, Tylenol’s initial manufacturer, conducted studies in the 1990s in an effort to innovate a safer alternative, but those efforts proved unsuccessful.

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