Acetaminophen—commonly sold as Tylenol—has long been a go-to option for pain and fever during pregnancy, but scientists have debated whether it could subtly influence fetal development and birth outcomes. In new research led by environmental scientists at the UNC Gillings School of Global Public Health, researchers report that typical prenatal use shows no statistically significant links to when a baby is born or how much the baby weighs at birth.
The study was published in the American Journal of Epidemiology and draws on a large U.S. pregnancy cohort drawn from the National Institutes of Health’s Environmental influences on Child Health Outcomes (ECHO) program. The investigators examined more than 8,900 mother-infant pairs to assess whether acetaminophen taken during pregnancy corresponded with differences in gestational age and birth size indicators.
Rather than focusing on a single outcome, the team analyzed four key measures of neonatal health: preterm birth risk, birth weight, small-for-gestational-age (SGA) status, and large-for-gestational-age (LGA) status. This approach helps clarify whether acetaminophen might shift the distribution of growth rather than simply changing average values.
Overall, the researchers found that acetaminophen use during pregnancy was not associated with meaningful differences in gestational age, average birth weight, or SGA status. About 59% of participating mothers reported using acetaminophen during pregnancy, providing substantial exposure variation for statistical evaluation.
The most notable signal emerged when birth weight was considered in relation to gestational timing. After accounting for whether infants fell into LGA versus non-LGA categories, prenatal acetaminophen use was linked to lower odds of being large-for-gestational-age. Importantly, this pattern did not translate into broader changes in preterm birth or average weight.
The findings offer a data-driven layer of reassurance for clinicians and patients who rely on acetaminophen as one of the few over-the-counter analgesics widely considered compatible with pregnancy. Still, the authors emphasize that epidemiologic studies cannot fully resolve questions about dose, timing, and specific health pathways that could operate beyond birth outcomes.
As researchers continue to refine exposure measurement and explore mechanisms, the practical takeaway remains conservative: acetaminophen should be used according to medical guidance, and any medication—prescription or otherwise—should be discussed with a healthcare professional.
Subject of Research: Prenatal over-the-counter acetaminophen use and birth outcomes
Article Title: Prenatal over-the-counter acetaminophen use and birth outcomes in the ECHO Cohort
News Publication Date: 21-May-2026
Web References: https://academic.oup.com/aje/advance-article/doi/10.1093/aje/kwag110/8689459
References: 10.1093/aje/kwag110
Image Credits: Not provided
Keywords: acetaminophen, Tylenol, pregnancy, birth outcomes, ECHO cohort, gestational age, birth weight, LGA, SGA, epidemiology
