Poor Uterine Contractility as Maternal Predisposition to Postpartum Hemorrhage Among Low-Risk Women: An Analysis of Large-Scale Database

Abstract

Background Postpartum hemorrhage (PPH) is a major cause of maternal mortality. Even seemingly low-risk women may suddenly develop postpartum hemorrhage, and these cases are often unpredictable and threatens maternal life. We hypothesized that innate poor uterine contractility may be a risk factor of PPH. In this study, we examined the association between the innate poor uterine contractility, suggested by the characteristics of labor and PPH in obstetrically low-risk women.Methods We used the Japan Perinatal Registry database of the Japan Society of Obstetrics and Gynecology registered in 2013–2016. With exclusion of women with well-known risk factors for PPH (maternal basal disease of hematologic disease, uterine leiomyoma, pregnancy by assisted reproductive technology, placenta abruption, placenta accrete, low-lying placenta, hypertensive disorders of pregnancy, macrosomia, polyhydramnios, or epidural analgesia), we analyzed 174,082 primiparous women who had one live singleton birth via vaginal delivery in cephalic presentation at 37 weeks’ gestation. Information about abnormal labor patterns (hypotonic uterine dysfunction, prolonged labor, and arrest of labor) diagnosed by obstetricians were also used in this study. In order to focus on innate maternal poor uterine contractility, we classified subjects into four classes according to whether they were diagnosed with abnormal labor patterns and whether they had used uterotonics, and Odds ratios and their 95% CI were calculated as well.Results Among the enrolled women, 10,508 (6.0%) had PPH. Abnormal labor patterns, including hypotonic uterine dysfunction (adjusted OR 1.28, 95% CI 1.22 to 1.34), prolonged labor (adjusted OR 1.41, 95% CI 1.30 to 1.52) and arrest of labor (adjusted OR 2.02, 95% CI 1.78 to 2.29) were significantly associated with an increased risk of PPH. Compared to women who were not diagnosed any abnormal labor patterns and did not use any uterotonics, women who were diagnosed with abnormal labor patterns were at a significantly increased risk for PPH regardless of whether they had used uterotonics(adjusted OR 1.23, 95% CI 1.10 to 1.37) or not (adjusted OR 1.30, 95% CI 1.23 to 1.37).Conclusion Our study suggests that innate poor uterine contractility is a significant predisposing risk factor in otherwise low-risk women.Trial Registration: This study is retrospectively registered.