Postpartum hemorrhage, defined as blood loss of ≥1000 mL within 24 hours after birth, is a leading cause of maternal morbidity and is associated with substantial financial and emotional burden. Based on societal and regulatory guidelines, in 2019, our institution adopted a postpartum hemorrhage prevention and management bundle based on the California Maternal Quality Care Collaborative initiatives. The study aimed to compare the prevalence of maternal blood product transfusion before and after the implementation of the bundle. This was a retrospective cohort study comparing the prevalence of blood product transfusion before and after the implementation of a California Maternal Quality Care Collaborative-based postpartum hemorrhage management bundle at a single safety net teaching hospital between October 2017 and December 2019 excluding a 4-month rollout period between September 2018 and December 2018. The study included all patients ≥18 years of age and at >20 weeks' gestation. Exclusion criteria were out-born deliveries, delivery at time of significant nonobstetrical trauma, and refusal of blood transfusion. The primary outcome was the frequency of any blood product transfusion in the pre- and postbundle implementation cohorts. Secondary outcomes included blood product transfusion type and amount, maternal death, intrauterine balloon placement, uterine artery embolization, unplanned peripartum hysterectomy, intensive care admission, and length of stay among all deliveries complicated by postpartum hemorrhage. We further evaluated compliance with bundle measures for all postpartum hemorrhage cases. Cohort characteristics were compared using chi-square tests or Fisher exact tests for categorical data and Satterthwaite or Wilcoxon 2-sample tests for continuous variables based on data distributions. The proportion of blood product transfusion were evaluated using a chi-square test. A total of 6744 deliveries were included with 3310 in the pre- and 3425 in the postbundle cohort. The prevalence of any blood product transfusion was similar between the pre- and postbundle cohorts (3.41%; 113/3310 vs 3.47%; 119/3425; P=.892). The prevalence of postpartum hemorrhage was 7.05% (233/3310) in the prebundle cohort and 10.34% (354/3434) in the postbundle cohort (P<.001). Among women with postpartum hemorrhage, those in the prebundle cohort had a higher rate of blood product transfusion than those in the postbundle cohort (36.05%; 84/233 vs 26.84%; 95/354; P=.018). Compared with the prebundle counterparts, patients with postpartum hemorrhage in the postbundle cohort had higher rates of utilization of intrauterine balloon placement (10.30%; 24/233 vs 16.95%; 60/354; P=.024). There were no significant differences among other secondary outcomes. The overall compliance with the bundle among those with blood loss ≥1000 mL was 92.1%. The implementation of the postpartum hemorrhage bundle did not decrease the overall prevalence of blood product transfusion and may have led to higher rates of utilization of resources.