2nd Circuit to Hear Oral Arguments in Tylenol-Autism MDL Appeal on October 6
On September 9, 2025, the U.S. Court of Appeals for the Second Circuit announced it will hear oral arguments on October 6, 2025, in the appeal of the multidistrict litigation (MDL No. 3043) alleging that prenatal exposure to acetaminophen (the active ingredient in Tylenol) causes autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) in children. The appeal challenges U.S. District Judge Denise Cote’s 2023 and 2024 rulings that excluded plaintiffs’ expert testimony and dismissed all federal claims, potentially reviving or ending the consolidated lawsuits against Johnson & Johnson (via its spin-off Kenvue), Walmart, CVS, Walgreens, and other retailers. This development comes amid heightened scrutiny from a forthcoming U.S. Department of Health and Human Services (HHS) report under Secretary Robert F. Kennedy Jr., which may explore links between prenatal Tylenol use and rising autism rates.
Background: The Tylenol-Autism Litigation
The lawsuits, centralized in the Southern District of New York since October 2022, involve over 600 families claiming that manufacturers and retailers failed to warn about risks of in utero acetaminophen exposure. Plaintiffs cite epidemiological studies suggesting a 20-300% increased risk of ASD and ADHD, based on meta-analyses from institutions like Harvard, Johns Hopkins, and Mount Sinai. For instance, a 2021 JAMA Pediatrics study found prolonged prenatal acetaminophen use associated with higher ASD odds, while a 2024 Mount Sinai review linked it to neurodevelopmental issues.
Defendants, including Kenvue (Tylenol’s maker), argue no causal link exists, pointing to the FDA’s longstanding approval of acetaminophen as safe during pregnancy and the American College of Obstetricians and Gynecologists’ guidelines. They claim the suits are preempted by federal law, as labels comply with FDA regulations.
Key Rulings Leading to the Appeal
- December 2023 Daubert Ruling: Judge Cote excluded all five of plaintiffs’ general causation experts, finding their testimony unreliable under the Daubert standard for scientific admissibility. She criticized the experts for relying on observational studies without establishing biological plausibility or causation, stating, “The experts’ opinions are not the product of reliable principles and methods.”
- August 2024 Dismissal: Without admissible expert evidence, Cote granted summary judgment to defendants, dismissing the entire MDL. She noted the ruling likely ends federal claims unless appealed successfully.
- Preemption Disputes: Earlier, Cote denied motions to dismiss based on federal preemption, rejecting arguments that FDA oversight bars state failure-to-warn claims. Defendants like Walmart sought interlocutory appeals, but these were denied.
Plaintiffs filed their notice of appeal in November 2024, arguing Cote misapplied Daubert by disregarding peer-reviewed methodologies and overemphasizing FDA policy over scientific consensus. A ruling is not expected until early 2026, potentially delaying proceedings for 2-3 years if remanded.
HHS Report and Broader Context
The appeal’s timing coincides with HHS’s “Make America Healthy Again” initiative, led by Kennedy, who has long advocated investigating environmental factors in autism. On September 9, 2025, Kennedy announced a report flagging prenatal Tylenol as a potential risk factor, alongside low folate levels, based on emerging data mining from the $50 million Autism Data Science Initiative. The report, set for release later in September, reviews over 100 research proposals and could bolster plaintiffs’ arguments, though Kenvue maintains “no causal link” exists and labels are FDA-compliant.
Autism diagnoses have risen sharply— from 1 in 150 children in 2000 to 1 in 36 in 2023 per CDC data—fueling litigation. However, the FDA and medical bodies emphasize acetaminophen’s safety, with no required pregnancy warnings beyond general consultation advice.
State Court Developments and Future Implications
While the federal MDL stalls, plaintiffs are shifting to state courts in California, Illinois, New Jersey, Pennsylvania, and Delaware, where the Frye standard (general acceptance in the scientific community) may allow more lenient expert admissibility than Daubert. For example:
- A California case (Davey v. Kenvue) is advancing toward trial with new experts.
- Illinois filings use Frye to admit evidence excluded federally.
If the Second Circuit reverses Cote’s rulings, the MDL could be reinstated, potentially leading to bellwether trials and settlements estimated at $50,000–$500,000 per case. A affirmance would likely end federal litigation, pushing all claims to fragmented state proceedings. Attorneys continue accepting cases, citing ongoing studies like a 2025 Harvard analysis showing 2-3x elevated risks.
Parents whose children were diagnosed with ASD or ADHD after prenatal Tylenol exposure may still pursue claims; consultations with firms like Marin, Barrett & Murphy or TorHoerman Law are recommended before statutes of limitations expire (typically 2-3 years from diagnosis in many states).