To analyze the relationship between blood loss volume and the etiologies as well as risk factors of severe postpartum hemorrhage (sPPH), providing a basis for developing and optimizing targeted preventive measures.

A retrospective study was conducted on clinical data from 683 patients with sPPH admitted to Shenzhen Maternity and Child Healthcare Hospital between January 2018 and December 2022. Patients were stratified into three groups based on blood loss volume: Group A (1 000~1 499 ml, n=385), Group B (1 500~2 499 ml, n=183), and Group C (≥2 500 ml, n=115). The causes of sPPH, relevant prenatal and intrapartum factors, multivariate analysis, and adverse pregnancy outcomes were analyzed.

Among the 683 sPPH cases, the etiologies were uterine atony (7.91%, 54/683), placental factors (38.51%, 263/683), birth canal laceration (5.42%, 37/683), and coagulopathy (4.25%, 29/683). Group A: 255 cases (66.23%) of uterine atony and 99 cases (25.71%) of placental factors; Group B: 81 cases (44.26%) of uterine atony and 81 cases (44.26%) of placental factors; Group C: 18 cases (15.65%) of uterine atony and 83 cases (72.17%) of placental factors. The differences in the distribution of both uterine atony and placental factors among the groups were statistically significant ( χ²=96.478 and 84.216, respectively; both P<0.001). Univariate analysis identified 15 factors associated with the severity of sPPH: maternal age ≥40 years, gestational age, primigravida, multiparity, history of intrauterine procedures, previous cesarean delivery(≥1), conception via assisted reproductive technology(ART), placenta accreta, placenta previa, pregnancy with uterine scar, cesarean delivery, and pre-delivery levels of hemoglobin, fibrinogen, serum calcium, and creatinine. Logistic regression revealed four independent factors for sPPH: placenta accreta (OR=4.386, 95%CI: 2.765~6.956, P<0.001), number of previous cesarean deliveries (OR=1.441, 95%CI: 1.016-2.043, P<0.05), ART conception (OR=1.512, 95%CI: 1.047~2.183, P<0.05), and pre-delivery fibrinogen level (OR=0.811, 95%CI: 0.659~0.998, P<0.05). As blood loss increased, the rates of blood transfusion (52.47%, 90.71%, 100.00%; χ²=144.865), ICU admission (18.44%, 54.64%, 93.04%; χ²=387.123), hemorrhagic shock (0.52%, 4.37%, 10.43%; χ²=28.988), and hysterectomy (0.26%, 0, 13.91%; χ²=74.392) showed a significant upward trend (all P<0.001).

Uterine atony was the primary cause of sPPH, but the proportion of placental factors increased with greater blood loss. Placenta accreta, number of previous cesarean deliveries, and ART conception were independent risk factors for sPPH, while pre-delivery fibrinogen level served as a protective factor. Early recognition, diagnosis, intervention, and comprehensive management are essential to improve maternal outcomes.