Objective: To compare the number of units of red blood cells (RBCs) transfused in patients with placenta accreta spectrum (PAS) treated with or without a multidisciplinary algorithm including placental uterine arterial embolisation (P-UAE) and a selective use of delayed hysterectomy. Design: Retrospective review Setting: Tertiary care hospital, United States, 2001-2018 Population: Women with histologically-confirmed PAS delivered after 24 weeks gestation Methods: Comparison of transfusion outcomes among PAS cases managed with versus without a multidisciplinary algorithm. To improve the equity of comparison, analyses were made separately among scheduled and unscheduled cases. Subjects were assigned to one of four cohorts: scheduled/per-algorithm, scheduled/off-algorithm, unscheduled/per-algorithm, or unscheduled/off-algorithm. P values were adjusted for multiple testing. Main outcome measures: RBCs transfused and estimated blood loss (EBL). Secondary outcomes included peri-operative complications and intensive-care unit admissions. Results: 87 subjects were identified: 36 treated per-algorithm (30 scheduled, 6 unscheduled), 51 off-algorithm (24 scheduled, 27 unscheduled). Among scheduled deliveries, 9 (30.0%) subjects treated per-algorithm received RBCs, compared to 20 (83.3%) subjects treated off-algorithm (p<0.01), with a median (interquartile range[IQR]) of 3.0 (2.0, 4.0) and 6.0 (2.5, 7.5) units transfused (p=0.13), respectively. Among unscheduled deliveries, 5 (83.3%) subjects treated per-algorithm were transfused RBCs compared to 25 (92.6%) off-algorithm (p=0.47), with a median (IQR) of 4.0 (2.0, 6.0) and 8.0 (3.0, 10.0) units transfused (p=0.47), respectively. Peri-operative complications were similar between cohorts. Conclusions: A multidisciplinary algorithm including P-UAE and selective use of delayed hysterectomy is associated with a lower rate of blood transfusion in scheduled but not unscheduled cases.