Key Takeaways: In a nationwide cohort study in Taiwan, positive associations between maternal acetaminophen prescriptions during pregnancy and attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) in offspring became null in sibling-matched analyses. However, further analyses in the sibling-matched analysis suggested the presence of unaddressed sources of bias, preventing firm conclusions from being drawn. The American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine have affirmed the safety and benefit of acetaminophen use during pregnancy for pain and fever.