Differential Effects of Epidural Analgesia on Modes of Delivery and Perinatal Outcomes between Nulliparous and Multiparous Women: A Retrospective Cohort Study

BACKGROUND Epidural analgesia is considered one of the most effective methods for pain relief during labor. However, it is not clear whether similar effects of epidural analgesia on the progression of labor, modes of delivery, and perinatal outcomes exist between nulliparous and multiparous women. METHODOLOGY/PRINCIPAL FINDINGS A retrospective cohort study was conducted to analyze all deliveries after 37 weeks of gestation, with the exclusion of pregnancies complicated by multiple gestations and fetal anomalies and deliveries without trials of labor; these criteria produced a study population of n=16,852. A multivariable logistic regression model was constructed to control for confounders. In total, 7260 of 10,175 (71.4%) nulliparous and 2987 of 6677 (44.7%) multiparous parturients were administered epidural analgesia. The independent factors for intrapartum epidural analgesia included a low prepregnancy body mass index, genetic amniocentesis, group B streptococcal colonization of the genito-rectal tract, and augmentation and induction of labor. In the nulliparous women, epidural analgesia was a significant risk factor for operative vaginal delivery (adjusted odds ratio [OR] 2.14, 95% confidence interval [CI] 1.80-2.54); however, it was a protective factor against Caesarean delivery (adjusted OR 0.62, 95% CI 0.55-0.69). Epidural analgesia remained a significant risk factor for operative vaginal delivery (adjusted OR 2.17, 95% CI 1.58-2.97) but not for Caesarean delivery (adjusted OR 1.09, 95% CI 0.77-1.55) in the multiparous women. Furthermore, the women who were administered epidural analgesia during the trials of labor had similar rates of adverse perinatal outcomes compared with the women who were not administered epidural analgesia, except that a higher rate of 1-minute Apgar scores less than 7 was noted in the nulliparous women who were administered epidural analgesia. CONCLUSIONS/SIGNIFICANCE Intrapartum epidural analgesia has differential effects on the modes of delivery between nulliparous and multiparous women, and it is not associated with adverse perinatal outcomes.