Crew resource management methods, initially developed in aviation, have been proposed as a means to reduce human errors in medicine through improved teamwork and communication. In this cluster-randomized trial, physicians and nurses on obstetrics wards underwent teamwork training based on the MedTeams model, which has been previously studied in the emergency department. The intervention did not result in improvement in patient (maternal or fetal) clinical outcomes or in the delivery of appropriate process measures. The authors ascribe this negative result to problems noted in other cluster-randomized trials of quality improvement interventions, such as inadequate time to implement the intervention, a relatively short follow-up period, and baseline variation between hospitals in the incidence of adverse events.