Postpartum haemorrhage trends in Sweden using the Robson ten group classification system: a population-based cohort study.

OBJECTIVE To examine postpartum haemorrhage (PPH) trends in Sweden using the Robson classification system. DESIGN Population-based cohort study. SETTING Sweden. POPULATION Deliveries in 2000-2016, classified as Robson groups 1-5 (singleton pregnancies in vertex presentation, from gestational weeks 37+0; n = 1 590 178). METHODS We examined temporal trends in PPH between 2000 and 2016 overall, and within each Robson group, and performed logistic regression to examine the influence of changes in risk factors (maternal, comorbidity, obstetric practice and infant factors) over time. MAIN OUTCOME MEASURES Postpartum haemorrhage, defined as an estimated blood loss of >1000 ml. RESULTS The overall PPH rate increased from 5.4 to 7.3%, corresponding to a 37% (OR 1.37, 95% CI 1.32-1.42) increase over time. Rates varied between Robson groups, ranging from 4.5% in group 3 to 14.3% in group 4b. Increasing trends in PPH were found in all Robson groups except for groups 2b and 4b (prelabour caesarean deliveries). In the unstratified analysis, adjusting for maternal, comorbidity and obstetric practice factors slightly attenuated the risk of PPH in the later period (2013-2016), compared with the reference period (2000-2004; crude OR 1.26, 95% CI 1.24-1.29, adjusted OR 1.22, 95% CI 1.20-1.25). Within individual Robson groups, changes in risk factors did not explain increasing rates of PPH. CONCLUSIONS Postpartum haemorrhage rates varied between Robson groups. Changes in risk factors could not explain the 37% increase in PPH for women in Robson groups 1-5 in Sweden, 2000-2016. TWEETABLE ABSTRACT Changes in risk factors could not explain the increasing trend of PPH in Sweden, and rates of PPH varied widely between Robson groups.