Study: The Largest Pregnancy Analysis Yet Finds No Tylenol-Autism Link
A sibling-matched analysis of more than 700,000 Hong Kong mother-child pairs found no association between acetaminophen use during pregnancy and autism, ADHD, or intellectual disability, at any trimester, dose, or frequency of use.
The study, published in JAMA Internal Medicine by researchers at the University of Hong Kong and Aston University, is the largest of its kind. It compared siblings born to the same mother to strip out the genetic and household factors that complicated earlier research linking Tylenol in pregnancy to neurodevelopmental outcomes in children.
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The sibling comparison design matters because children with autism or ADHD are more likely to have a family history of those conditions. Earlier observational studies compared unrelated children and could not fully separate whether acetaminophen use was the cause or whether mothers who used more acetaminophen were more likely to carry genes associated with neurodevelopmental differences in the first place. Matching siblings controls for that confounding.
Acetaminophen is the most commonly used over-the-counter pain reliever during pregnancy. It crosses the placenta and has been the subject of increasing regulatory and public concern since a 2021 consensus statement from a group of researchers called for precautionary restrictions. That statement, and subsequent coverage amplified by the current administration, led many pregnant women to avoid it even when facing fever or moderate pain, both of which carry their own risks in pregnancy.
Fever during pregnancy, particularly in the first trimester, is associated with neural tube defects and other adverse fetal outcomes. Unmanaged pain affects sleep, cortisol, and blood pressure. The precautionary framing around acetaminophen has had real downstream effects on pregnant women’s decisions about whether to treat those conditions.
This study does not eliminate every question about acetaminophen in pregnancy, but it is the strongest evidence to date that the neurodevelopmental concern is not supported by the data. The clinical guidance from major obstetric organizations has not changed: acetaminophen remains the recommended first-line pain reliever during pregnancy when one is needed.