Abstract
BACKGROUND: Postpartum hemorrhage (PPH) remains a leading cause of maternal morbidity and mortality worldwide. It is therefore important to improve our understanding of the risk factors for PPH according to parity, in particular, those linked to modifiable obstetric practices. The aim of this study was to assess the risk of PPH by the duration of the second and third stages of labor, stratified by parity. METHODS: This study was based on secondary analysis of data from participants in a randomized controlled trial. A sample of women from three university hospitals in France aged at least 18 years, with a singleton pregnancy, in the first stage of labor, at 36-42 weeks of gestation, with epidural anesthesia and a vaginal delivery were included. The main outcome was PPH rates, defined by blood loss > 500 mL within 2 h after delivery. Characteristics of mothers, newborns, labor, and delivery, and their relation to PPH were explored with multivariable regression models. RESULTS: Of 1598 women included, 864 were nulliparous and 680 parous; their respective PPH rates were 9.1% (79/864) and 7.4% (54/680) (P = 0.2), and the overall rate 8.3% (133/1598). The multivariable analysis found that PPH was associated with the durations of both oxytocin exposure (aOR 1.10, 95%CI 1.01-1.20) and the third stage of labour (aOR 1.80, 95%CI 1.37-2.38) among nulliparous women, and the PPH risk increased with both duration of the third stage (aOR 2.10, 95%CI 1.56-2.83) and history of PPH (aOR 3.02, 95%CI 1.38-6.59) among parous women. CONCLUSIONS: The duration of oxytocin exposure was found to be a risk factor for PPH among nulliparous women as was a history of PPH among parous women. Future studies should focus on duration of third stage of labor, especially when active management of the third stage of labor (AMTSL) is routinely used. TRIAL REGISTRATION: The trial was registered at ClinicalTrials.gov NCT01113229.