A federal appeals court has breathed new life into hundreds of lawsuits filed by parents who say their children developed autism or ADHD after exposure to Tylenol in the womb. The 2nd U.S. Circuit Court of Appeals overturned part of a lower court's decision that had thrown out the cases, ruling that a federal judge overstepped by weighing the science herself rather than letting juries hear the evidence.
The unanimous ruling, handed down Tuesday by a three-judge panel, reinstated testimony from three expert witnesses for the plaintiffs, experts from Harvard, Columbia, and the Albert Einstein College of Medicine. Their testimony had been excluded by U.S. District Judge Denise Cote, a Clinton appointee who dismissed the consolidated lawsuits in December 2024.
The decision reopens a legal front that could force acetaminophen manufacturers to answer for what parents say is a failure to warn pregnant women about potential risks. And it arrives at a moment when the question of Tylenol's safety during pregnancy has moved from courtrooms into the White House itself.
The panel was careful to draw boundaries around its ruling. The court stated plainly in its opinion:
"These appeals concern what qualifies as admissible epidemiological testimony in support of a general causal relationship. We are not deciding whether there is a general causal relationship between acetaminophen and ADHD and/or ASD. We are also not deciding whether the manufacturers of acetaminophen must warn consumers about any alleged risk posed by such a potential causal relationship."
In other words, the court did not rule that Tylenol causes autism. It ruled that a trial judge cannot substitute her own scientific judgment for the jury's when qualified experts disagree.
That distinction matters. Judge Cote had concluded that the plaintiffs' experts relied on unreliable scientific evidence. She went further with the lead expert, Andrea Baccarelli, the dean of the Harvard T.H. Chan School of Public Health, writing that he had "cherry-picked and misrepresented study results." The appeals court found that characterization went too far, crossing the line from gatekeeping into fact-finding that belongs to a jury.
Three witnesses had their testimony restored by the ruling. Baccarelli, the Harvard dean, had previously testified that "substantial evidence" supports a causal relationship between frequent, high-dose acetaminophen use during pregnancy and neurodevelopmental disorders in children. Eric Hollander, a psychiatry professor at the Albert Einstein College of Medicine, and Brandon Pearson, a toxicologist at Columbia University, round out the trio.
These are not fringe figures. They hold positions at some of the most prestigious research institutions in the country. Whether their conclusions ultimately hold up under cross-examination is a question for trial, which is precisely the point the appeals court made.
During oral arguments, Judge Gerard Lynch observed that "reasonable scientists do appear to disagree" on the question, suggesting that disagreement within the scientific community should not automatically bar expert testimony from reaching a jury.
The scale of the litigation is significant. More than 500 lawsuits against Tylenol maker Kenvue are now revived by the ruling. Each represents a family alleging that a product marketed as safe, and widely recommended by obstetricians, harmed their child.
Doctors and medical societies still consider acetaminophen the preferred treatment for pain and fever during pregnancy. No firm scientific consensus has established a causal link to autism. But the existence of observational studies raising questions, combined with the credentials of the experts involved, was enough for the appeals court to say the cases deserve their day in court.
The ruling leaves open major questions. Which specific parts of Judge Cote's December 2024 decision survived the appeal? What happens next procedurally, do the cases return to Cote's courtroom, or get reassigned? The opinion does not appear to address those details, and the defendants in the lawsuits were not named in reporting on the decision.
The legal fight now unfolds against an unusual political backdrop. In September, President Trump publicly urged pregnant women to avoid Tylenol, saying:
"Don't take Tylenol. Don't take it. If you just can't, I mean, fight like h*** not to take it."
HHS Secretary Robert F. Kennedy Jr. joined Trump in urging pregnant women to steer clear of acetaminophen whenever possible. Neither statement carried the force of a regulatory action, but coming from the president and the nation's top health official, they sent a signal that the federal government takes the concern seriously.
The American College of Obstetricians and Gynecologists pushed back sharply. Its president, Dr. Steven Fleischman, called the suggestions irresponsible:
"Suggestions that acetaminophen use in pregnancy causes autism are not only highly concerning to clinicians but also irresponsible when considering the harmful and confusing message they send to pregnant patients, including those who may need to rely on this beneficial medicine during pregnancy."
Fleischman added that such claims "dangerously simplify the many and complex causes of neurologic challenges in children." That's a fair point about the complexity of autism's origins. But it also sidesteps the narrower question the courts are now grappling with: whether the existing evidence is strong enough that juries, not judges, not medical societies, should weigh it.
The tension between federal health leadership and the medical establishment on pregnancy-related safety questions is not limited to Tylenol. Courts have also been active on other fronts involving reproductive health, including a recent Fifth Circuit decision on mail-order abortion pills that raised its own set of questions about safety standards during pregnancy.
Strip away the politics and the medical debate, and this case comes down to a principle conservatives have long championed: courts should not substitute their judgment for the people's. The jury system exists precisely for disputes where qualified experts land on different sides. A trial judge who excludes all of one side's evidence because she finds the other side's science more persuasive has effectively decided the case herself.
That is what the appeals court found Judge Cote did. Her December 2024 ruling did not merely apply evidentiary standards, it reached conclusions about which scientific findings were correct. The appeals panel, unanimously, said that crossed a line.
The three judges on the panel were all Democratic appointees, which makes the ruling harder to dismiss as ideologically motivated. They applied the rules of evidence as written and found the lower court wanting. Whatever one thinks about the underlying science, the procedural point is sound.
None of this means the plaintiffs will win at trial. Acetaminophen manufacturers will have every opportunity to challenge the experts' methodology, question their conclusions, and present their own evidence. The playing field has simply been leveled, the cases will proceed on the merits rather than dying on a judge's desk.
The ruling sends a clear message to trial courts handling complex scientific litigation: your job is to evaluate whether expert methodology is reliable, not to pick winners in active scientific debates. That standard protects plaintiffs and defendants alike.
For the families involved, the decision means the fight continues. Hundreds of parents who believe their children were harmed will now have a chance to make their case before a jury. The science may or may not support them. But they will get to argue it, which is all the legal system is supposed to guarantee.
When judges start deciding which science is settled and which questions the public is allowed to ask, the courtroom stops being a place where ordinary people can seek accountability. The 2nd Circuit, to its credit, pushed back.
