Department of Health and Human Services Links Prenatal Tylenol Use to Autism: Expanding Litigation Risks for Manufacturers, Retailers, Distributors, and Clinicians
On September 22, 2025, the Department of Health and Human Services (HHS) released a report highlighting alleged consistent associations between in utero acetaminophen (Tylenol) exposure and later diagnoses of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). On the same day, President Trump and HHS Secretary Robert F. Kennedy, Jr. announced a series of federal actions in response to these findings, including a directive for the Food and Drug Administration (FDA) to initiate a safety label change for Tylenol (and the generic equivalents) and the launch of a nationwide public service campaign to inform families and protect public health.
HHS Report. Although the HHS report acknowledges conflicting sibling-comparison data and states that causation is not definitively established, it references large cohort studies that show allegedly consistent linkages between acetaminophen and neurodivergence. In particular, the Boston Birth Cohort study—referenced in the HHS report—measured acetaminophen and its metabolites in umbilical cord plasma at birth to determine evidence of fetal exposure. The study allegedly found a significant, dose-dependent association between higher levels of cord acetaminophen metabolites and increased risk of both ASD and ADHD. However, HHS and FDA reiterate that short-term, appropriate dosing remains widely regarded as safe, particularly for the treatment of fever, which itself carries risks during pregnancy.
FDA Label Change. The FDA has initiated the process for a label change of acetaminophen products (including Tylenol) to reflect evidence indicating that use of acetaminophen during pregnancy may be linked to a higher risk of neurological disorders, such as autism and ADHD. This announcement was coupled with the FDA’s Notice to Physicians urging clinicians to minimize the use of acetaminophen during pregnancy for routine low-grade fevers. The Notice emphasizes the need for clinicians to exercise their best judgment, balancing the potential risks of acetaminophen exposure with the fact that acetaminophen is the safest over-the-counter option in pregnancy among all analgesics and antipyretics. The Notice further states that a causal relationship between acetaminophen and autism has not yet been established and there are studies to the contrary.
Expanding Litigation. Plaintiffs are already litigating in this space, as seen in the federal multidistrict litigation (MDL), In re Acetaminophen—ASD/ADHD Products Liability Litigation, No. 22-md-3043 (S.D.N.Y.). Plaintiffs have filed master complaints against Johnson & Johnson Consumer Inc. (the maker of Tylenol prior to Kenvue spinning off in 2023) and retailers and marketers of store-brand acetaminophen, alleging failure to warn, negligence, negligent misrepresentation by omission, breach of implied warranty, and design defect based on inadequate warnings. In 2023, the court granted Daubert motions excluding all five of plaintiffs’ expert witnesses, impacting approximately 550 pending cases, due to methodological flaws and unreliable opinions that diverged from scientific consensus. Plaintiffs appealed and the Second Circuit is set to hear the case on November 17, 2025. On September 25, 2025, both parties filed letters to the Second Circuit in response to President Trump’s announcement. Plaintiffs noted that federal officials allegedly relied on the analysis of one of their excluded experts, Dr. Baccarelli, when urging minimized Tylenol use and initiating labeling changes—arguing that excluding his testimony and affirming the Daubert ruling would “pose grave separation of powers concerns.”
They contend expert evidence credited by the executive branch readily meets Rule 702 and should be heard by a jury. Defendants counter that the FDA expressly stated no causal relationship has been established, and Dr. Baccarelli’s own public statement framed the evidence as an “association” requiring further research—positions they say align with the lower court’s finding that plaintiffs’ causation opinions are unreliable. Thus, defendants argue there is no conflict with the government’s actions and no separation-of-powers issue.
It is reported that Kenvue (the current maker of Tylenol) is preparing for an explosion of litigation since the new federal warning could unleash thousands of additional filings, particularly in state courts, even if the federal MDL is not revived. In most instances, the statute of limitations for claims on behalf of minors is tolled until the child turns 18, meaning filings could continue for years and materially expand potential exposure for manufacturers, retailers, and other defendants. New claims may also emerge against clinicians for professional negligence and lack of informed consent, particularly where providers recommended or reassured long-term or frequent use of acetaminophen during pregnancy without disclosing disputed associations and alternatives. The FDA’s new guidance and public service campaign may be cited to argue that the standard of care has shifted and that providers should have discussed the evolving evidence and recommendations.
Additionally, consumer protection and false advertising claims may target “pregnancy-safe” messaging by manufacturers, retailers, and pharmacy chains, while employers and third-party payors could pursue reimbursement and economic loss claims based on alleged concealment of risks and elevated long-term care costs. The HHS report may also give rise to medical monitoring and derivative claims that include requests for surveillance programs for exposed children and parents’ loss-of-consortium and bystander claims where permitted.
Industry Response. However, the recent federal activity is not without pushback. The American College of Obstetricians and Gynecologists (ACOG) directly disputes recent claims and regulatory suggestions that link prenatal acetaminophen exposure to neurodevelopmental disorders. ACOG alleges that, after more than two decades of research, no reputable study has established a causal relationship. The most rigorous studies, including large sibling-controlled cohort studies, have allegedly found no significant association between prenatal acetaminophen exposure and increased risk of autism, ADHD, or intellectual disability. ACOG points out that studies suggesting a link often suffer from significant methodological flaws, such as reliance on self-reported data, lack of control for confounding genetic or familial factors, and inconsistent outcome assessments. Furthermore, ACOG stresses that untreated maternal conditions for which acetaminophen is indicated—such as fever, pain, and headaches—can themselves cause significant harm to both mother and fetus, including increased risk of birth defects.
As the leading professional organization for obstetricians and gynecologists, ACOG’s statements are highly influential in both clinical and legal contexts, and its position is supported by other major organizations such as the Society for Maternal-Fetal Medicine. In ongoing and future litigation regarding acetaminophen’s alleged link to ASD or ADHD, ACOG and similar organizations may be well positioned to provide amicus curiae briefs that summarize the current state of scientific evidence on causal links, emphasize the clinical necessity and safety of acetaminophen, and warn against the public health risks of restricting access to this medication.
The National Institutes of Health (NIH) Autism Data Science Initiative has also announced that it will fund new research into autism prevalence, etiology, treatment, and services as part of the federal response. The results of these studies may further inform future litigation and regulatory actions.
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Mayer Brown’s Product Liability & Mass Torts team advises manufacturers, retailers, distributors, and healthcare providers on litigation strategy, warning and promotional reviews, crisis response, and MDL coordination. We are closely monitoring filings and developments following the HHS announcement.
For further information or assistance navigating the HHS’s report linking prenatal acetaminophen use to autism, please contact the authors: Mike Olsen (molsen@mayerbrown.com), Hank Bullock (hbullock@mayerbrown.com), Niketa Patel (npatel@mayerbrown.com), Victoria Bell Lowry (vbell@mayerbrown.com), Samantha Bellina (sbellina@mayerbrown.com), or your usual firm contact.
