For a long time, parents and doctors have debated whether acetaminophen, often recognized under the brand name Tylenol, might be tied to autism or other developmental issues in children. However, in spite of the recent alarm bells going off, doctors are reassuring parents that Tylenol/acetaminophen is considered safe for expectant mothers. 

In a statement to Parents, Tylenol’s parent company, Kenvue said, “We believe independent, sound science clearly shows that taking acetaminophen does not cause autism. We strongly disagree with any suggestion otherwise and are deeply concerned with the health risk this poses for expecting mothers.”

Adding weight to that argument is a recent Swedish study, one of the largest ever done on this question, that tracked millions of children and found no solid evidence linking the medicine to autism, ADHD, or intellectual disability.

The study, published in JAMA in April 2024, looked at nearly 2.5 million children born between 1995 and 2021. Early results suggested there might be a small increased risk in kids whose mothers used acetaminophen. But when researchers dug deeper, comparing brothers and sisters with the same parents, the risk disappeared.

“By comparing siblings born to the same mother, we can control for many indications as well as early life environmental factors that might influence the relationship that we are studying,” explains Brian Lee, PhD, an epidemiologist at Drexel University’s Dornsife School of Public Health and the study’s lead author. “When we compared the full siblings, we saw no difference in risk between the exposed siblings and the unexposed siblings.”

That kind of sibling comparison, sometimes called sibling analysis, is important because it strips away many of the outside influences that can make a study look like it’s showing a connection when it really isn’t.

These results challenge earlier research that hinted at possible links between acetaminophen and developmental conditions. Experts now say those older studies may have been skewed by “confounding factors,” which are outside variables that can make two things look related when they’re not.

“This study is a very important response to concerns from the previous studies,” says Karen Keough, MD, a pediatric neurologist and medical director at Pediatrix Medical Group in Austin, Texas. She was not part of the research team.

The American College of Obstetricians and Gynecologists (ACOG) has also weighed in before, stressing in 2021 that there was “no clear evidence that proves a direct relationship between the prudent use of acetaminophen during any trimester and fetal developmental issues.”

So where does that leave parents-to-be? Experts say acetaminophen is still one of the safest pain and fever reducers to use during pregnancy. It’s also far safer than options like ibuprofen or aspirin, which aren’t recommended at all while expecting.

“Fever, in particular, can be dangerous to the developing baby’s brain and should be controlled, especially in early pregnancy, and pain relief might be essential for many situations,” Dr. Keough explains.

Dr. Lee adds that while the Swedish study wasn’t designed as a safety guarantee, it should reassure expectant parents who worry that they may have harmed their child by taking Tylenol.