A federal appeals court has revived more than 500 lawsuits against Tylenol maker Kenvue, ruling that a district judge improperly excluded expert testimony from three prominent doctors, including the dean of Harvard’s School of Public Health, who linked prenatal acetaminophen use to autism and ADHD in children. The 2nd U.S. Circuit Court of Appeals in Manhattan, in a 64 page decision authored by Judge Guido Calabresi, found that the testimony reflected methodologies used by other scientists and “constitute acceptable interpretations of scientific evidence where scientists may, and in fact do, disagree.” The ruling returns the cases to U.S. District Judge Denise Cote for further proceedings, sending Kenvue shares down 1.8% and raising the stakes in what plaintiffs’ lawyers describe as potentially one of the largest litigations in American history.
The legal battle sits at the intersection of science, politics, and corporate liability. The lawsuits, consolidated into a multidistrict litigation in New York, allege that Johnson & Johnson and retailers including CVS, Kroger, Target, Walgreens, and Walmart failed to warn pregnant women that acetaminophen, the active ingredient in Tylenol, could increase the risk of neurodevelopmental disorders in their children. The plaintiffs’ experts included Harvard public health dean Andrea Baccarelli, Albert Einstein College of Medicine psychiatry professor Eric Hollander, and Columbia University toxicologist Brandon Pearson. In December 2024, Judge Cote dismissed all cases, criticizing the experts’ methodology as unreliable. The appeals court disagreed, finding that the district court had set too high a bar for admissibility and that scientific disagreement alone does not render expert opinions invalid. Calabresi emphasized that the court was not deciding whether acetaminophen causes autism or ADHD, only that the plaintiffs’ experts met the threshold for presenting their theories to a jury.
The case gained political prominence after President Donald Trump and Health and Human Services Secretary Robert F. Kennedy Jr. held a September 2025 press conference warning pregnant women to avoid acetaminophen unless medically necessary, citing the alleged link. The White House announced that the FDA would issue safety label changes and launch a public service campaign. However, global health officials pushed back forcefully, the European Medicines Agency stated there was “no link” between paracetamol use during pregnancy and autism, while the World Health Organization noted that evidence “remains inconsistent” and cautioned against drawing causal conclusions. UK Health Secretary Wes Streeting told citizens to “not pay any attention whatsoever to what Donald Trump says about medicine,” and Australian regulators joined the rejection of the claims. The researchers whose work Trump cited, including Baccarelli himself, clarified that their studies showed an association, not causation, with one Mount Sinai study author telling The New York Times, “We cannot answer the question about causation.”
Kenvue, which was spun off from Johnson & Johnson in 2023 and agreed last November to a $40 billion acquisition by Kimberly-Clark, maintains that Tylenol is safe and that “credible, independent science shows no proven link” between acetaminophen and neurodevelopmental disorders. The company plans to challenge the reliability of the plaintiffs’ experts at trial. Medical societies continue to consider acetaminophen the preferred treatment for pain and fever during pregnancy, noting that untreated fever itself poses risks to both mother and fetus. With the lawsuits now heading back to district court for discovery and potential bellwether trials, the pharmaceutical industry faces a precedent setting test of whether correlation in epidemiological studies can translate into billions of dollars in liability. For the estimated 65% of pregnant women who have used acetaminophen, the case raises profound questions about informed consent, scientific uncertainty, and the boundaries of corporate responsibility for products marketed as safe during pregnancy.
