A new study has determined that using acetaminophen, the active ingredient in Tylenol, during pregnancy does not increase the risk of autism, ADHD, or intellectual disability in children.
Published in the journal JAMA, the study analyzed the prenatal and medical records of approximately 2.5 million children born in Sweden from 1995 to 2019.
Researchers from the Karolinska Institute in Sweden and Drexel University conducted the study, which used statistical models to compare children exposed to acetaminophen during pregnancy with those who were not.
Initially, the analysis indicated a slight increase in the risk of autism, ADHD, and intellectual disability among the exposed group.
However, when the researchers conducted sibling analyses — comparing outcomes between full sibling pairs who share the same biological parents — they found no evidence of increased risk associated with acetaminophen use during pregnancy.
Sibling analyses are particularly robust because they account for shared genetic and environmental factors among siblings, thereby reducing potential biases present in conventional clinical trials.
Dr. Eric Brenner, an assistant professor of pediatrics at Duke University not involved in the study, highlighted the strength of sibling controls:
“Sibling controls will most likely grow up in the same home, have similar diets, and will be exposed to similar environments which allows investigators to better control for environmental factors.”
“This is a very extensive and well-designed study that found no association between acetaminophen use and neurodevelopmental impairment, including autism and ADHD,” Brenner added.
“While any medication should always be used judiciously and in consultation with an obstetrician, it appears that acetaminophen is safe.”
The findings challenge recent research and assertions linking acetaminophen use during pregnancy to heightened risks of neurodevelopmental disorders.
While regulatory bodies such as the US Food and Drug Administration and the European Medicines Agency have considered acetaminophen to pose minimal risks during pregnancy, some previous studies and expert groups have advised caution, recommending limited use unless medically necessary.
The study authors underscored the role of confounding factors in previous research, explaining that associations observed in other studies may have been influenced by factors such as parental neurodevelopmental disorders, which are highly heritable and may influence both medication use and child outcomes.
The study also observed significant differences between parents who used acetaminophen more frequently during pregnancy and those who did not.
Factors such as lower socioeconomic status, higher early pregnancy body mass index, smoking during pregnancy, and diagnoses of psychiatric or neurodevelopmental conditions were more prevalent among parents with higher acetaminophen use.
While the study found no increased risk associated with other painkillers like aspirin, NSAIDs, and opioids in sibling analyses, aspirin use was unexpectedly linked to a reduced risk of neurodevelopmental disorders. However, further investigation is needed to confirm this finding.
Dr. Yalda Afshar, an assistant professor at UCLA, emphasized the importance of consulting healthcare professionals regarding the use of any medications, prescription or over-the-counter, during pregnancy.
She expressed hope that the study’s findings would reassure pregnant individuals who require acetaminophen for pain relief or fever reduction.
“Acetaminophen is one of the most commonly used and well-studied medications in pregnancy and is considered safe to use judiciously for reducing fever and pain,” Brenner reiterated.
