Masarwa R, et al. - Via searching MEDLINE, Embase, Scopus, and the Cochrane Library up to December 2018, researchers evaluated the role of potential unmeasured confounding in the estimation of the connection between acetaminophen (eg paracetamol, Tylenol) use during pregnancy and the risk of ADHD, by bias analysis, as well as evaluated the roles of selection bias and exposure misclassification. The risk ratio (RR) for attention deficit hyperactivity disorder (ADHD) was 1.35 when adjusted estimates were pooled across all studies. Bias analysis suggests that the previously reported correlation between the use of acetaminophen during pregnancy and an increased risk of ADHD in offspring may be attributable to unmeasured confounding. There is limited capacity to infer a causal relation.