Lawyers representing dozens of pregnant women who allege that taking acetaminophen caused developmental or behavioral problems in their babies asked a panel of federal judges in St. Louis to consolidate their cases in multidistrict litigation (MDL), Bloomberg reported Sept. 29. 

As of late September, 87 complaints had been filed in seven states against Walmart, CVS, Walgreens and other drugstore giants that sell their own branded version of acetaminophen, which is the main active ingredient in Tylenol and hundreds of over-the-counter and prescription medicines, used primarily to treat pain and fever, according to the Food & Drug Administration (FDA). 

The claims were filed after new studies linked the drug to autism, attention-deficit disorder/hyperactivity disorder and other developmental and behavioral problems in infants. The plaintiffs blame their children’s behavior and/or neurological problems on high doses of acetaminophen that they took while they were pregnant, and blame the sellers of the drug for not issuing a warning about the risk. 

More than 20 peer-reviewed studies conclude that there is an association between high acetaminophen use and developmental problems, including a 2018 study published in the American Journal of Epidemiology, which concluded that “Acetaminophen use during pregnancy is associated with an increased risk for ADHD, [Autism Spectrum Disorder], and hyperactivity symptoms.” The study is quick to note, however, that the study is only observing data collected by others and “is susceptible to several potential sources of bias.”

Walmart and the other drug sellers as well as groups representing physicians maintain acetaminophen is safe and dispute the findings in the research studies, calling it inconclusive and showing no direct causation. 

The number of claims could skyrocket because millions of women have taken acetaminophen while pregnant, and autism is one of the fastest-growing childhood conditions, although the U.S. Centers for Disease Control and Prevention has stated that it is unclear whether this is a true increase in the prevalence of autism or the result of a broader definition of ASD and better efforts in diagnosis. The developmental disability affects roughly 1 in 100 children worldwide, and its prevalence has increased by nearly 180% since 2000, according to The Autism Community in Action (TACA). 

Bloomberg reports that autism affects one in every 44 kids who are 8 years old. Researchers are not sure why rates have increased. Case reports for other developmental disorders and attention disorders are also on the rise. 

Thus far, plaintiffs have not named Johnson & Johnson—the largest manufacturer of acetaminophen—as a defendant, nor any of the approximately 600 drug makers that produce it.