Objective: To determine the impact of the Obstetric Simulation Training and Teamwork (OB‐STaT) curriculum on postpartum haemorrhage (PPH) rates and outcomes. Design: Before‐and‐after study. Setting: Maternity care hospitals within the USA. Population: Patients who delivered between February 2018 and November 2019. Methods: Interprofessional obstetric teamwork training (OB‐STaT) conducted at each hospital. Electronic medical records for deliveries were reviewed for 6 months before and after conducting OB‐STaT at participating hospitals. Main outcome measures: The PPH rate (blood loss of ≥1000 ml), uterotonic medications used, tranexamic acid use, blood product transfusion, hysterectomy, length of stay and composite maternal morbidity (postpartum haemorrhage, hysterectomy, transfusion of ≥4 units of blood products and intensive care unit admission for PPH). Results: A total of 9980 deliveries were analysed: 5059 before and 4921 after OB‐STaT. The PPH rates did not change significantly (5.48% before vs 5.14% after, p = 0.46). Composite maternal morbidity decreased significantly by 1.1% (6.35%–5.28%, p = 0.03), massive transfusions decreased by 57% (0.42%–0.18%, p = 0.04) and the mean postpartum length of stay decreased from 2.05 days (1.05 days SD) to 2.01 days (0.91 days SD) (p = 0.04). Following OB‐STaT, haemorrhage medication use increased by 36% (14.8%–51.2%, p = 0.03), the use of tranexamic acid for PPH treatment almost doubled (2.7%–4.8%, p < 0.001) and the rate of hysterectomy significantly increased (0%–0.1%, p = 0.03). Conclusions: Although the PPH rates did not decrease, OB‐STaT significantly improved maternal morbidity, decreased massive transfusions, and improved PPH management by increasing the utilization of uterotonic medications, tranexamic acid and hysterectomy. [ABSTRACT FROM AUTHOR]