SUMMARY Cesarean deliveries (cesareans), when used judiciously, save lives. However, research indicates that the use of cesareans in the United States (US) has risen well above the level of necessity and has become a contributor to maternal morbidity and mortality. Patients who have cesareans face increased risk of serious complications such as amniotic fluid embolism, catastrophic hemorrhage, placental abnormalities in future pregnancies, and death. Babies born by cesarean face increased risk of respiratory complications, and, emerging research suggests, chronic disease. For these reasons, the Healthy People 2020 goal is to reduce cesarean rates to ≤ 23.9% for first-time mothers. Currently, over one-third of all women giving birth in the United States deliver via cesarean. Hospital cesarean rates across the US range from 6% to 69%, and significant variation remains even when controlling for patient clinical factors and hospital and patient demographics. Patient request for a cesarean make up less than 1% of cesareans nationwide, and, thus, cannot explain this variation. Our prior work has found that this variation in practice is associated with labor and delivery unit culture and, moreover, that successful reduction in cesarean overuse correlates with specific aspects of unit culture, such as decreased fear of vaginal birth, physician acceptance of oversight, agreement with evidence-based practices, and belief in the importance of maternal agency. Organizational culture has been shown to be a key element in reducing variation in hospital outcomes in other clinical areas; and, underscoring its importance, the national safety bundle addressing cesarean overuse charges hospitals to “develop a unit culture that supports vaginal birth.” Unfortunately, there is evidence that this aspect of quality improvement receives the least attention from hospitals that participate in initiatives to reduce cesarean overuse. After 2 years of a California statewide initiative, about 42% of hospitals still had cesarean rates over the Healthy People 2020 goal. This is not surprising given that few tools and no rigorously designed user- centered tools exist to help hospitals implement culture change. This proposal leverages the strength and support of multiple state-level perinatal quality collaboratives at different stages of implementation and a novel, continually improving Labor Culture Survey tool. We will engage in a comprehensive user-centered design process to create, adapt, and implement a “Culture Change Toolset” for use in hospital-based, organizational culture quality improvement efforts to reduce cesarean overuse. Furthermore, we will incorporate patient perspectives and feedback as key stakeholders in the design and adaptation process. Based on our prior data, a 1-point improvement in unit culture supportive of vaginal birth would convert 331,773 cesarean deliveries or 27% of US cesarean births and 9% of all US births each year to vaginal deliveries and th...