The Effect of Inter-Pregnancy Interval on Primary Postpartum Hemorrhage in Urban South Ethiopia: A Community-Based Matched Nested Case Control Study

Abstract Background: Globally, postpartum hemorrhage remained a leading cause of maternal mortality, accounting for nearly one quarter of all pregnancy related deaths. To decrease postpartum hemorrhage related maternal mortalities to desired level, identifying its risk factors is very crucial to guide interventions. In this regard, little is known about the link between inter-pregnancy interval and primary postpartum hemorrhage in Ethiopia where maternal mortality is one of the highest in the world (412 per 100,000 live births). Therefore, we mainly aimed to assess the effect of inter-pregnancy interval on primary postpartum hemorrhage in urban South Ethiopia.Methods: A community-based matched nested case control study was conducted among 365 women (73 cases and 292 controls). Cases were women with primary postpartum hemorrhage and controls were women without primary postpartum hemorrhage. Cases were individually matched with controls (1:4 ratio) for age group and location. A conditional logistic regression analysis was done using R version 4.0.3 software. Statistically significant association was declared at P < 0.05. Odds ratio and attributable fraction (AF) were used to report effect sizes from the adjusted model.Results: The incidence of primary postpartum hemorrhage was 2.9%, 95%CI: (2.2%, 3.6%). More than half (56%) of primary postpartum hemorrhage was attributed to short inter-pregnancy interval <18 months (AF=56.1%, 95%CI: 6.5%, 79.5%). This could have been prevented if inter-pregnancy interval was increased to 24-36 months. Moreover, primary postpartum hemorrhage was attributed to presence of antepartum hemorrhage (AF=82.4%, 95% CI: 17.4%, 96.2%), prolonged labour (AF=71.8%, 95%CI: 31.5%, 88.4%) and late initiation of breast feeding (AF=78.2%, 95%CI: 47.4%, 90.9%).Conclusions: In this study, inter-pregnancy interval was causally related with primary postpartum hemorrhage. More than half of primary postpartum hemorrhage can be prevented by spacing pregnancy for at least 18 months. Other risk factors for primary postpartum hemorrhage were antepartum hemorrhage, prolonged labour and late initiation of breast feeding. Increasing existing maternal health service utilization (family planning emphasizing on spacing, antenatal care, health facility delivery with early referrals and postnatal care) will contribute for reducing primary postpartum hemorrhage, as the risk factors identified were maternal health service related and modifiable.