Taking acetaminophen – known in the US by the brand name Tylenol – during pregnancy has no effect on later autism diagnoses, according to a sweeping new study from Denmark published Monday.

The Trump administration has targeted Tylenol use in pregnancy as a major cause of autism in children, which appears to have led to a drop in pregnant people taking the pain reliever.

Through Denmark’s robust national healthcare system, researchers were able to track more than 1.5 million children ‌born between 1997 and 2022 in the national health registry, including 31,098 children who were exposed to Tylenol in utero.

Autism was diagnosed in 1.8% of children who were exposed to Tylenol and 3% of those who weren’t, according to the study, which was published in Jama Pediatrics. A similar 2024 study in Sweden found a marginal link that disappeared after taking siblings into account, suggesting that autism is strongly genetic, which has already been demonstrated in other studies.

A US review of existing studies in 2025 found a potential relationship, but it wasn’t clear whether confounders were at play. For instance, if pregnant autistic people take Tylenol more often than neurotypical pregnant people because of higher pain levels.

Health officials announced in September 2025 that the US Food and Drug Administration (FDA) would initiate a label change for acetaminophen, warning of a potential link to autism. Trump cautioned several times against taking the pain reliever during pregnancy.

“​​If you’re pregnant, don’t take Tylenol,” Trump said at a press conference at the time. “Don’t take Tylenol. Don’t have your baby take Tylenol.” He said the medication is “not good” and taking Tylenol during pregnancy is associated with “a very increased risk of autism”.

Trump added that in some “medically necessary” cases, acetaminophen might still be recommended in pregnancy. “That’s, for instance, in cases of extremely high fever that you feel you can’t tough it out,” he said.

At the same September press conference, officials announced that leucovorin, a B vitamin, could be used to treat autism. That claim was quietly walked back earlier this year.

Tylenol is safe to take during pregnancy and can play a key role in relieving pain and bringing down fevers. Yet after the September announcement, Tylenol use among pregnant women in emergency rooms dropped by 10%, according to a Lancet study published last month.