Reassuring evidence on acetaminophen’s safety during pregnancy keeps growing.
A large, two-decade study in Hong Kong is the latest to find no link between use of the drug — known as Tylenol in the United States — and a risk of autism or attention-deficit/hyperactivity disorder in children. The lack of an association persisted no matter the trimester the drug was prescribed, the dose or the recommended frequency, researchers report June 29 in JAMA Internal Medicine.
Joining several other analyses, including ones conducted in Sweden and Japan, the research adds to the body of evidence reporting no association between acetaminophen use in pregnancy and long-term neurodevelopmental disorders in children.
All the studies compared siblings born to mothers who had taken the drug at some point, such that some siblings were exposed to the drug in utero and others weren’t. This approach accounts for the fact that both ADHD and autism are largely influenced by genetics. If acetaminophen were also a factor, researchers would expect a difference between siblings exposed to the drug and those not. None of the studies have found one.
For the new study, the researchers pored over electronic health records from 2001 to 2023 for more than 700,000 pairs of mothers and children. Around 43 percent of the kids encountered acetaminophen in utero. The team focused on pairs of siblings that differed in exposure and used their records to follow the children for at least two years for autism diagnoses and at least five for ADHD. The autism analysis included more than 124,000 children, while the ADHD component had more than 97,000. Going a step further, the analysis also looked at the timing and amount of acetaminophen that was prescribed.
Acetaminophen is the first and safest choice for fever or pain relief during pregnancy, according to the American College of Obstetricians and Gynecologists. In 2025, the Trump administration, without evidence, impugned the safety of the drug at a news briefing that included inaccurate information about autism.
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