Postpartum hemorrhage in singleton births in Iceland 2013-2018, incidence proportion and risk factors

INTRODUCTION: Many countries have reported an increased incidence proportion of postpartum hemorrhage (PPH). The proportion might also have increased at the National University Hospital of Iceland, based on the registration of the ICD-10 code O72. This study aimed to assess the incidence proportion and risk factors for >_1000 ml PPH in singleton births in Iceland 2013-2018. METHODS: This population-based cohort study included data from the Icelandic Birth register on 21.110 singleton births in 2013-2018. Incidence proportion of PPH was assessed based on three definitions: PPH >500 ml, PPH >_1000 ml, and O72. Binomial regression was used to assess both the change in the proportion of >_1000 ml PPH over time, stratified by maternal BMI, and risk factors for >_1000 ml PPH. RESULTS: There was an inconsistency in the proportion of PPH when defined by blood loss >500 ml and O72. In obese women, PPH >_1000 ml was more than twice as likely in those delivering in 2018 compared with 2013 (OR 2.23; CI 1.35-3.81). The strongest risk factors were emergency cesarean (OR 2.68; CI 2.22-3.22) and instrumental delivery (OR 2.18; CI 1.80-2.64), but macrosomia, primiparity and BMI >_30 were also independent risk factors.CONCLUSION: The incidence proportion of >_1000 ml PPH has increased among obese women. The detrimental health effects of obesity and the increased prevalence of interventions among these women could explain these results. It is necessary to use registered blood loss in milliliters in the Icelandic Birth Register because of the under-registration of the diagnostic code O72.