A mounting body of evidence shows that the use of acetaminophen—widely known by its brand name Tylenol—during pregnancy may pose risks to the fetus and to early childhood development. That was the conclusion of a new review study on which I was a lead author. Acetaminophen, which has the chemical name paracetamol, is a go-to over-the-counter medication that’s widely recommended by doctors to relieve pain and reduce fever. Our study, based on an assessment of 25 years of research in the areas of human epidemiology, animal studies, and in-vitro studies, concludes that prenatal acetaminophen exposure may increase the risks of reproductive organs developing improperly. We identified a heightened risk of neurodevelopmental disorders, primarily attention deficit hyperactivity disorder and related behaviors, but also autism spectrum disorder, language delays, and decreased IQ. In our consensus statement—a broad agreement by our multidisciplinary international panel of experts—published in Nature Reviews Endocrinology in September, 91 …