A study on the association between different delivery modes and pelvic floor muscle strength in women during early postpartum period

Abstract

Background/objectives Pelvic floor dysfunction (PFD) arises from factors such as degeneration and trauma, leading to weakened pelvic floor fascia, ligaments, perineum, adjacent muscles, and other supporting structures in women. Clinically, PFD manifests as stress urinary incontinence (SUI), pelvic organ prolapse (POP), and abnormal pelvic floor muscle strength, substantially impairing women's health. This study investigated the association between pelvic floor electromyography results in postpartum women at 6–8 weeks after delivery and various pregnancy- and childbirth-related factors, with the aim of identifying determinants of impaired pelvic floor function during the early postpartum period. Methods A retrospective analysis was performed on 1,154 postpartum women who delivered at the Obstetrics Department of Zhongshan Hospital, Dalian University, and underwent pelvic floor electromyography 6–8 weeks postpartum. Participants were classified into the vaginal delivery group (n = 802) and the cesarean section group (n = 352) based on delivery mode. The analysis examined differences in early postpartum pelvic floor muscle strength between the two delivery modes and identified factors influencing pelvic floor muscle strength in each group. Results Electrical activity of pelvic floor muscles in both the fast- and slow-twitch phases was lower in the vaginal delivery group compared with the cesarean section group, whereas resting-phase values before and after contraction were higher in the cesarean section group. In the vaginal delivery group, independent risk factors for early postpartum pelvic floor muscle strength impairment included pregnancy weight gain > 16 kg, second-stage labor duration ≥ 2 h, advanced maternal age at first birth, episiotomy, perineal laceration, and gestational hypertension. In the cesarean section group, pregnancy weight gain ≥ 11.5 kg, pre-pregnancy BMI > 24 kg/m², gestational hypertension, premature rupture of membranes, preeclampsia, history of uterine fibroids, and full-term delivery were identified as independent risk factors. Conclusions Both delivery modes are associated with changes in early-postpartum pelvic-floor muscle electromyographic activity. Altered EMG suggestive of impaired muscle activation is observed more prominently among women after vaginal delivery, while greater changes in resting pelvic-floor muscle tone are noted in the cesarean-delivery group. Cesarean delivery, therefore, does not eliminate the risk of impaired pelvic-floor muscle function or the development of PFD.