Science remains mixed on prenatal acetaminophen and autism as HHS readies report

Robert F. Kennedy Jr.’s Department of Health and Human Services plans to release a report this month that, according to The Wall Street Journal, will link prenatal exposure to acetaminophen and certain vitamin deficiencies to autism spectrum disorder. An HHS spokesperson told the New York Post that the agency is “using gold‑standard science” and that claims about the report’s contents are speculative until the final document is released.

Autism is a complex neurodevelopmental condition characterized by differences in social communication, repetitive behaviors and focused interests. Federal estimates indicate autism affects about one in 31 children in the United States, and diagnoses have increased substantially in recent years, with federal figures showing a 175% jump from 2011 to 2022.

Acetaminophen, sold commonly as Tylenol in the United States and as paracetamol elsewhere, is an over‑the‑counter pain reliever and fever reducer widely used during pregnancy to treat maternal pain and fever. Scientists do not fully understand its mechanism of action. Researchers have long examined environmental, genetic and perinatal factors that may contribute to autism risk; suggested environmental contributors have included advanced parental age, infections during pregnancy, birth complications and certain medications taken during pregnancy.

Published studies to date present mixed findings on a link between prenatal acetaminophen exposure and neurodevelopmental outcomes. A large Swedish cohort study published in 2024 that followed nearly 2.5 million children found no causal relationship between maternal acetaminophen use during pregnancy and later neurodevelopmental disorders such as autism or attention deficit hyperactivity disorder. By contrast, an analysis led by researchers at the Icahn School of Medicine at Mount Sinai published in 2025 reviewed 46 studies and reported an association between prenatal acetaminophen exposure and an increased risk of autism and ADHD. The Mount Sinai authors cautioned that the body of evidence does not yet establish causation and suggested several potential biological mechanisms, including oxidative stress, hormonal interference and genetic alterations that could affect fetal brain development.

The Mount Sinai team recommended “judicious acetaminophen use — lowest effective dose, shortest duration — under medical guidance, tailored to individual risk‑benefit assessments, rather than a broad limitation,” in their BMC Environmental Health paper.

Some researchers have argued that observed associations could stem from confounding by indication — that is, factors related to why a woman took acetaminophen, such as fever or infection during pregnancy, may themselves affect neurodevelopmental risk. Obstetric professional groups maintain guidance reflecting available evidence. The American College of Obstetricians and Gynecologists continues to regard acetaminophen as safe for pregnant women, while advising expectant mothers to consult their clinicians before taking any medication.

A spokesperson for Kenvue, the maker of Tylenol, told the Wall Street Journal the company “continues to believe there is no causal link between acetaminophen use during pregnancy and autism.” Financial markets reacted after the WSJ report, with Kenvue shares falling more than 14% on the day the story was published. Several Tylenol‑related lawsuits alleging links to autism have been dismissed by courts citing insufficient scientific evidence.

Experts and public‑health officials say further research is needed to determine whether associations observed in some studies reflect a causal effect, confounding factors, bias in study design or chance. Until more definitive evidence emerges, medical organizations advise pregnant people to discuss pain and fever management with their health care providers to weigh the benefits of treating maternal symptoms against any potential risks to fetal development.