Some bits and pieces from AI
Observational studies using large population data have found a statistical association between a mother's prolonged acetaminophen use during pregnancy and a slightly increased risk of ASD and ADHD in children.
A review, co-authored by Harvard T.H. Chan School of Public Health Dean Andrea Baccarelli and published in Environmental Health in August 2025, also highlighted an association between prenatal acetaminophen use and neurodevelopmental disorders. They emphasize that correlation does not equal causation, and the link is likely due to other confounding factors.
A 2024 study in JAMA examined health records for nearly 2.5 million children in Sweden, including sibling pairs.
While initial models without sibling controls showed a marginal increase in risk, the association disappeared when researchers compared siblings where one was exposed to acetaminophen in the womb and the other was not.
The sibling-comparison method is considered more reliable because it controls for shared genetic and environmental factors that are difficult to measure in other types of studies.
It also needs to be noted that the slight association was found with prolonged use -- i.e., more than 10 days and some more than 4 weeks. Having ruled out acetaminophen as a causal agent, the general speculation is that the correlation may be related to the underlying condition the expectant mother was taking the acetaminophen to manage.
And it should also be noted, that pain increases cortisol as part of the stress response, as well as chemicals that have their own associated risks. An uncontrolled fever presents a risk too.