Tylenol autism lawsuit revived as appeals court sends cases back to trial

A courtroom battle over whether taking acetaminophen-based painkillers during pregnancy can cause autism in children has reignited in the United States.

The Wall Street Journal reported that the US Court of Appeals for the Second Circuit in New York on Monday sent back to a lower court a group of related lawsuits that had been dismissed for insufficient evidence.

The cases were brought by families who claim their children were diagnosed with autism or attention deficit hyperactivity disorder after they took Tylenol during pregnancy, and who sued Kenvue, the maker of Tylenol. The trial court dismissed the suits, ruling that the plaintiffs' claims lacked credible scientific evidence. A key basis for that ruling was that reports submitted by experts — including Andrea Baccarelli, dean of the Harvard T.H. Chan School of Public Health — had selectively picked results favorable to the plaintiffs and could not be considered reliable.

The appeals court ruled that excluding the medical experts requested by the plaintiffs had been an improper overreach and that a jury should have been allowed to weigh the validity of their opinions, sending the cases back to the lower court. The Wall Street Journal said the appellate ruling clears the way for more than 500 similar lawsuits to again contest liability in court.

The controversy has also been stoked by the Trump administration. The administration had previously warned that acetaminophen — the active ingredient in the fever reducer and painkiller Tylenol — could cause autism, citing research by Baccarelli.

Until recently, acetaminophen had been considered virtually the only medication pregnant women could safely take to reduce fever and relieve pain. The Trump administration's claims to the contrary sparked fierce debate in the health and medical community. The WHO and the EU rebuffed those assertions as unfounded. The FDA also said a causal link between acetaminophen use and the birth of children with autism had not been established. Medical organizations including the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine also weighed in, saying acetaminophen use during pregnancy is safe, in an effort to defuse the situation.