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By Samuel López | USA Herald

Tylenol maker Kenvue and some of America’s largest pharmacy and retail chains are asking a federal appeals court to reconsider a decision that breathed new life into roughly 550 lawsuits alleging prenatal exposure to acetaminophen contributed to autism spectrum disorder or attention-deficit/hyperactivity disorder in children.

In a filing submitted Thursday, Kenvue and other defendants urged the U.S. Court of Appeals for the Second Circuit to revisit its July ruling overturning key parts of U.S. District Judge Denise Cote’s handling of the massive products-liability litigation. Defendants include Walgreens, CVS, Walmart, Target, Costco, Kroger, Albertsons and other retailers that sold Tylenol or store-brand acetaminophen products.

At its core, the latest fight is not simply about Tylenol. It is about who gets to decide when disputed science is reliable enough to reach a jury.

Judge Cote previously excluded testimony from five experts offered by plaintiffs to establish what lawyers call “general causation” — whether prenatal acetaminophen exposure is capable of causing autism or ADHD.

Without admissible expert evidence establishing that basic scientific proposition, Cote granted summary judgment for the defendants in approximately 550 cases.

But the Second Circuit concluded Cote went too far with three experts — Andrea Baccarelli, Eric Hollander and Brandon Pearson.

The appellate panel held that the experts used methodologies accepted within their scientific disciplines and that disagreements over how they interpreted the available research were, in significant part, matters that could be tested before a jury.

The court upheld Cote’s exclusion of two other experts, Robert Cabrera and Stan Louie. It also sent a related group of ADHD-only cases back for further consideration of expert Roberta Ness.

Kenvue and the retailers now argue that the Second Circuit weakened the role Congress and the federal evidence rules give trial judges in screening expert testimony.

Federal Rule of Evidence 702 requires the party offering expert testimony to demonstrate that the expert used reliable principles and methods and reliably applied those methods to the facts.

The defendants maintain that complicated and unsettled scientific questions cannot simply be passed to jurors whenever qualified experts disagree. They argue district judges are the “true gatekeepers” charged with preventing unreliable scientific opinions from reaching trial.

If the Second Circuit refuses to reverse its ruling outright, the companies alternatively want the court to clarify that the three experts’ opinions are not automatically admissible and allow Cote to conduct another Rule 702 review.

That distinction could have consequences well beyond Tylenol litigation. Rule 702 and the Supreme Court’s landmark Daubert decision govern expert testimony throughout federal litigation, including pharmaceutical, toxic-tort, environmental and medical-device cases.

Perhaps the most important part of the Second Circuit’s decision is what it did not decide.

The court expressly stated that it was not deciding whether acetaminophen causes autism or ADHD, whether manufacturers were legally required to provide additional warnings, or what public-health policy should be.

Instead, the court said the question was how aggressively a trial judge may scrutinize the conclusions of qualified scientists who are using generally accepted methodologies in an area where legitimate scientific disagreement exists.

In practical terms, allowing an expert to testify does not mean the expert is correct. It means the opinion clears the evidentiary threshold necessary to be presented, challenged through cross-examination and weighed against opposing experts.

Medical Evidence Remains Contested

The scientific issue remains highly sensitive, particularly for pregnant women deciding how to treat fever and pain.

The FDA currently states that it has not found clear evidence that appropriate acetaminophen use during pregnancy causes adverse neurobehavioral or developmental outcomes, while continuing to evaluate the evidence.

The American College of Obstetricians and Gynecologists likewise says the current weight of evidence does not support a causal link between prenatal acetaminophen use and neurodevelopmental disorders and continues to recommend acetaminophen as the preferred pain reliever and fever reducer during pregnancy when used appropriately.

For the families bringing these lawsuits, however, the Second Circuit ruling means their claims are no longer finished before reaching the deeper factual fight over causation.

For Kenvue and the retailers, the rehearing request is an effort to put that fight back behind the courthouse gate.

Sources:

Rutledge v. Walgreen Co., 24-916 (2d Cir. 2026)

About the Author

Samuel López is an independent reporter for USA Herald, where he has covered legal, insurance and investigative matters since 2022.

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