The women recruited into the study are shown compared with the number of women delivered during the study period as reported in the Cardiff Maternity Database. *The number of women experiencing bleeds of ≥2000 mL among all women delivering during the study period, according to data from the Cardiff Maternity Database, was 98. This is fewer than the number of women recorded as experiencing bleeds of this volume enrolled in the study (n = 100). **One woman was recruited but withdrew consent and is not included in the analyses. A precipitant was one of uterine atony, cesarean section, placental abruption, placenta previa, microvascular oozing, or cardiovascular instability (pulse >100 bpm or systolic blood pressure <100 mm Hg).