A large-scale Danish study, recently published in JAMA Pediatrics, has found no significant association between prenatal exposure to acetaminophen (commonly known as Tylenol) and the risk of autism spectrum disorder (ASD) in children. The comprehensive research, which analyzed data from over 1.5 million children, utilized a robust methodology including within-family comparisons to address previous concerns.
The study's findings indicate that "Tylenol exposure during pregnancy wasn't significantly related to autism risk within or between families," as highlighted in a recent social media post by Crémieux. This conclusion was reached despite the high quality of exposure measurement in Denmark, where approximately 80% of acetaminophen is prescription-based rather than over-the-counter.
Researchers, led by Kira Philipsen Prahm, MD, PhD, of Copenhagen University Hospital Rigshospitalet, examined children born in Denmark between 1997 and 2022. The study found no statistically significant link in either general population analyses (Hazard Ratio 1.03, 95% CI 0.95-1.12) or sibling-matched analyses (Hazard Ratio 1.09, 95% CI 0.91-1.27), which are crucial for controlling genetic and environmental confounding factors.
This new evidence comes amidst ongoing debate and past controversies surrounding the safety of acetaminophen use during pregnancy. In September 2025, the U.S. Food and Drug Administration (FDA) initiated a process for a label change to warn about a potential link, a move that drew criticism from medical groups who deemed it not evidence-based.
Experts like David Mandell, ScD, of the University of Pennsylvania Perelman School of Medicine, emphasized the importance of replication in science, noting that "what we look for is the confluence of evidence over multiple studies done by independent groups." This Danish study aligns with a 2024 Swedish study and a 2025 Japanese study, both of which also found no increased autism risk with prenatal acetaminophen exposure when sibling comparisons were employed.
The findings reinforce current medical guidelines, which generally consider acetaminophen a safe option for managing pain and fever during pregnancy when used at the lowest effective dose and only when necessary. While the study acknowledged a limitation in tracking over-the-counter acetaminophen use, previous simulations suggest such bias would be largely negligible.
