"No Evidence Linking Tylenol to Autism"... Conclusion from Analysis of 700,000 Mother-Child Pairs

Over 700,000 Mother-Child Pairs Analyzed Using Sibling Comparison
No Increased Risk Regardless of Timing or Dosage
"Stronger Evidence for the Safety of Tylenol Use During Pregnancy"

A large-scale study has found that taking acetaminophen (the active ingredient in Tylenol), a fever-reducing and pain-relieving medication, during pregnancy does not increase the risk of children developing autism spectrum disorder (ASD) or attention deficit hyperactivity disorder (ADHD).

A study has shown that taking the fever and painkiller acetaminophen during pregnancy does not increase the risk of autism spectrum disorder (ASD) or attention deficit hyperactivity disorder (ADHD) in children. Photo by Pixabay

According to Yonhap News on June 30, a research team led by Professor Eric Yuk Fai Wan at the University of Hong Kong and Professor Ian Chi Kei Wong at Aston University in the UK reported in the American Medical Association (AMA) journal 'JAMA Internal Medicine' that, after analyzing 708,020 mother-child pairs, they found no association between acetaminophen use during pregnancy and the risk of ASD or ADHD in children.

The research team utilized a sibling comparison approach in their analysis. Based on electronic medical records from Hong Kong's public healthcare system between 2001 and 2023, they established a cohort of 708,020 mother-child pairs. They then compared siblings who had different levels of exposure to the medication during pregnancy to analyze the risks of ASD (124,333 cases) and ADHD (97,285 cases). By comparing siblings who share genetic factors and family environment, they were able to control for confounding factors within the household.

The analysis showed that using acetaminophen during pregnancy was not associated with an increased risk of either ASD or ADHD in children. Even when the researchers analyzed the timing of use (first, second, or third trimester), the pattern of use (specific periods or the entire pregnancy), and cumulative dosage, no significant increase in risk was observed. However, in a standard cohort analysis—not using the sibling comparison—an association was observed between Tylenol use and increased risk of ASD and ADHD. Still, the same results were found for acetaminophen use before pregnancy, when the medication could not affect the fetus, suggesting that shared familial factors rather than the medication itself were likely responsible.

Acetaminophen is recommended worldwide as the first-line medication for treating pain and fever during pregnancy. However, concerns have been consistently raised because the drug crosses the placenta and could potentially affect fetal neurodevelopment. Some observational studies have also reported an association between acetaminophen use during pregnancy and an increased risk of ASD or ADHD in children.

The controversy spread to the political arena last year. On September 22, 2025, U.S. President Donald Trump stated at a White House briefing that "the U.S. Food and Drug Administration (FDA) will notify physicians that Tylenol use during pregnancy could greatly increase the risk of autism," repeatedly advising pregnant women to refrain from taking the medication. The FDA subsequently began procedures to change the drug's labeling.

In response to such claims, the research team stated, "This study further strengthens the evidence that acetaminophen exposure during pregnancy is not a major risk factor for ASD or ADHD in children." They emphasized, "While acetaminophen is a safe and essential pain reliever and antipyretic during pregnancy, alternatives such as nonsteroidal anti-inflammatory drugs (NSAIDs) or opioids are associated with well-known risks. This provides important evidence that using Tylenol during pregnancy when medically necessary is safe."

This content was produced with the assistance of AI translation services.