A two-decade sibling study using Hong Kong health records finds no association between acetaminophen use during pregnancy and autism or ADHD in children, with the lack of effect holding across trimester, dose, and dosing frequency.
On June 29. a new large study in Hong Kong landed with the kind of result many expect to see—and still the kind that keeps families up at night. In a paper published in JAMA Internal Medicine. researchers reported that acetaminophen use during pregnancy. known as Tylenol in the United States. showed no link to autism or attention-deficit/hyperactivity disorder in children.
The findings add to a growing body of research that has repeatedly failed to connect acetaminophen taken in pregnancy with long-term neurodevelopmental outcomes. What makes this study particularly persuasive is its design. The analysis compared siblings—children born to the same mother—where some siblings were exposed to acetaminophen in utero and others were not. That sibling approach matters because it helps account for the genetic influences that play a major role in both autism and ADHD.
In the new study. the researchers reviewed electronic health records spanning from 2001 to 2023 for more than 700. 000 pairs of mothers and children. Around 43 percent of the kids encountered acetaminophen in utero. To focus on the question of causality rather than just correlation. the team narrowed in on sibling pairs that differed in exposure and then tracked the children for autism diagnoses for at least two years and for ADHD diagnoses for at least five years.
The autism analysis included more than 124,000 children, and the ADHD component included more than 97,000. The lack of association persisted regardless of when the drug was prescribed during pregnancy, the dose, or the recommended frequency.
This result comes as the research landscape has been filled with additional sibling-based studies from other countries. Joining several other analyses—including ones conducted in Sweden and Japan—the new work adds to the body of evidence reporting no association between acetaminophen use in pregnancy and long-term neurodevelopmental disorders in children.
The logic behind these studies is direct: if acetaminophen were a contributing factor to autism or ADHD, then exposed siblings would show a difference compared with unexposed siblings. Across the studies, researchers have not found that difference.
One more detail sharpens the study’s message. For this Hong Kong analysis, the researchers didn’t stop at whether acetaminophen was used. The team also looked at the timing and amount of acetaminophen that was prescribed.
Outside the research world, acetaminophen has long had a clear clinical standing. Acetaminophen is the first and safest choice for fever or pain relief during pregnancy, according to the American College of Obstetricians and Gynecologists.
And yet, the tension around the drug’s reputation has lingered. In 2025, the Trump administration, without evidence, impugned the safety of the drug at a news briefing that included inaccurate information about autism.
For now. the new Hong Kong study lands as another checkpoint for families seeking reassurance with data they can test: in this record set. in these sibling comparisons. and across trimester. dose. and dosing frequency. acetaminophen exposure in pregnancy did not translate into higher rates of autism or ADHD in childhood.
acetaminophen Tylenol pregnancy autism ADHD JAMA Internal Medicine Hong Kong study sibling design electronic health records neurodevelopment
So… Tylenol is fine then?
Not surprised, everyone online was screaming about Tylenol but studies keep saying no link. My aunt took it her whole pregnancy and her kid is totally normal, like anecdotal but yeah.
Wait, the study says no autism link, but what about “other issues” like learning delays? Also 2001-2023 records doesn’t mean the dosing was accurate, like how do they even know the exact trimester? I feel like they just didn’t look hard enough.
They compared siblings so genetics is the same, cool, but moms don’t take Tylenol for no reason. Like if the pregnancy was rough or there was an infection, wouldn’t that mess with the brain stuff anyway? Either way this topic keeps getting dragged up every time someone finds a new TikTok. Let people sleep, jeez.