A cluster-randomized controlled trial was conducted at 7 intervention and 8 control hospitals to evaluate the effect of teamwork training on the occurrence of adverse outcomes and processes of care in labor and delivery. The intervention, called the Labor & Delivery Team Coordination Course, was a standardized teamwork training curriculum based on crew resource management that emphasized communication and team structure. The primary outcome was the proportion of deliveries at greater than or equal to 20 weeks gestation in which one or more adverse maternal and/or neonatal outcomes occurred (Adverse Outcome Index, AOI). Additional outcomes included 11 clinical process measures.