Two new large studies examine acetaminophen and ASD

A study by researchers in Denmark concludes that there is no evidence that maternal acetaminophen use during pregnancy increases the odds of a child having an autism spectrum disorder ASD, while the findings of a study by researchers in Taiwan—who examined data on both ASD and attention deficit/hyperactivity disorder (ADHD)—are less clear-cut.

In the first study, Kira Philipsen Prahm and colleagues analyzed data on more than 1.5 million children in Denmark. In addition to looking at autism rates in the overall group, the researchers performed a sibling analysis to account for lifestyle or hereditary factors that could influence their results.

The researchers found no increased likelihood of ASD in children whose mothers took acetaminophen during pregnancy, either in the general population or in sibling comparisons. In addition, the study found no link when looking at the data by trimester or by the amount of medication taken.

In the second study, Pei-Chen Lee and colleagues analyzed data from more than two million births in Taiwan, identifying mothers who received at least two acetaminophen prescriptions during pregnancy. (While acetaminophen is available over the counter at pharmacies in Taiwan, most people obtain it via free prescriptions.) They found that children of mothers who took acetaminophen during pregnancy had a 12% higher likelihood of developing ADHD and a 6% higher likelihood of developing ASD. The association was strongest for mothers with more frequent acetaminophen use or those who took higher daily doses.

However, when the researchers performed a sibling-matched analysis, comparing siblings from the same family, the link between acetaminophen use and ASD or ADHD disappeared. This suggests, they say, that familial factors, rather than acetaminophen use itself, could be responsible for the connection.

The researchers also examined their sibling data to see whether their results varied depending on whether an older or younger sibling was exposed to acetaminophen. They found that when only the older sibling was exposed, the odds of an ASD or ADHD diagnosis were higher. Conversely, when only the younger sibling was exposed, the likelihood of receiving an ASD or ADHD diagnosis was lower. They comment, “The substantial divergence in associations in the sibling design when assessing whether the older or the younger sibling was prenatally exposed to acetaminophen suggests that additional biasing issues undermine the validity and prevent firm conclusions from being drawn using the sibling design.”

Citations

“Acetaminophen exposure during pregnancy and the risk of autism in offspring,” Kira Philipsen Prahm, Pingnan Chen, Line Rode, Charlotte Kvist Ekelund, Karen Ruben Husby, Thomas Bergholt, Øjvind Lidegaard, Nikolai Madrid Scheller, and Anders Pretzmann Mikkelsen, JAMA Pediatrics, April 13, 2026 (online). Address: Kira Philipsen Prahm, Department Obstetrics, Center of Fetal Medicine, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark.

—and—

“A major pregnancy scare collapses: Tylenol shows no autism risk in more than 1.5 million children,” Sanjukta Mondal, Medical Xpress, April 16, 2026.

—and—

“Maternal acetaminophen use and child neurodevelopment,” Pei-Chen Lee, Yu-Hsuan Chuang, Ya-Hui Hu, Chia-Ni Lin, Chung-Yi Li, Ying-Yeh Chen, Julia E. Heck, Giselle Bellia, Haoran Zhuo, Onyebuchi A. Arah, and Zeyan Liew, JAMA Pediatrics, March 9, 2026 (free online). Address: Pei Chen Lee, Department of Public Health, College of Medicine, National Cheng Kung University, 138 Shengli Rd, Tainan 704, Taiwan, [email protected].

—and—

“Large-scale study challenges link between acetaminophen use during pregnancy and autism risk in children,” Sanjukta Mondal, Medical Xpress, March 11, 2026.