The weekend effect, in which adverse events occur more commonly outside of normal working hours, has been noted across multiple health care settings. In this retrospective observational study, investigators examined maternal and neonatal quality measures for deliveries occurring on Tuesdays compared with deliveries during the weekend. They found that four of seven performance measures studied were worse during the weekend, but staffing levels did not seem to explain the higher complication rate on weekends. This study is consistent with prior work suggesting patient safety vulnerabilities during the weekend, but further investigation of the weekend effect is required.