Grouping parturients by parity, previous cesarean and mode of delivery identifies parturients at risk for postpartum-hemorrhage

Abstract

Background: The prevalence of postpartum-hemorrhage varies between studies depending on the definition of postpartum-hemorrhage and the population studied. Significant differences are reported among sub-groups stratified by single risk factors including parity, mode of delivery and management of labor. Objective: Our primary goal was to form a clinical classification aimed to identify sub-groups of parturients at risk for postpartum-hemorrhage by combining clinical universal risk factors. Study design: Retrospective cohort including all women who delivered at Shaare Zedek Medical Center, an affiliated university medical center, managing 10% of national deliveries, between January 2006 and December 2014. Parturients were grouped according to three characteristics, all known as universal risk factors for PPH: parity (primiparous, multiparous), previous cesarean and mode of delivery (spontaneous vaginal delivery, instrumental delivery, non-planned and elective cesarean): P-C-MoD classification. All together the classification included 12 sub-groups. Postpartum-hemorrhage was defined as a decrease of ≤3 g% hemoglobin or transfusion of blood products and was calculated for each of the sub-groups independently. A univariate analysis followed by a multivariate analysis was performed to study the risk for postpartum-hemorrhage among the sub-groups studied, controlling for confounding factors including age, onset of delivery, number of fetus and fetal birth weight. Results: The crude rate of postpartum-hemorrhage, for all 126,693 parturients was 7%. The prevalence for PPH differed significantly between independent risk factors compared to the combined risk factors of the P-C-MoD classification. Among primiparous, the prevalence was 14%, this changed significantly when combining primiparous with mode of delivery, ranging from 11% for spontaneous vaginal delivery to 27% among those with instrumental delivery. The prevalence of PPH among multiparous varied between 3% (spontaneous vaginal delivery) and 20% (emergency CD). There was significant difference in the prevalence of PPH between the sub-groups of the P-C-MoD classification. Primiparous who underwent ID were at increased risk for PPH, approximately one of four women in this group (27%) experienced PPH. Applying a univariate analysis revealed that the risk for PPH was significantly increased for primiparous undergoing ID compared to all other sub-groups reaching an OR of 12.8 (95% CI: 11.9; 13.8) compared to multiparous undergoing SVD. Applying a multivariate analysis minimally altered the results. Conclusions: Grouping parturients by parity, previous cesarean and mode of delivery (P-C-MoD classification) is a useful tool to identify parturients at risk for postpartum-hemorrhage and is superior compared to single independent risk factors. Future studies are needed to confirm the external validity of this classification.