Assessment of the effects of different delivery methods on the pelvic floor muscle function in primiparous women by total pelvic floor ultrasound and surface electromyography

To investigate the effects of cesarean section (CS) and vaginal delivery (VD) on early postpartum pelvic floor muscle function via total pelvic floor ultrasound (TPFUS) and pelvic floor surface electromyography (sEMG).

A retrospective cross-sectional analysis was performed on 210 primiparous women with full-term singleton pregnancies who delivered at Wuhu Hospital of Traditional Chinese Medicine between July 2022 and December 2023. The participants were divided into the CS group (n = 57) and VD group (n = 153). All postpartum women underwent TPFUS and sEMG examinations 6–8 weeks after delivery. The primary outcomes included the incidence of pelvic organ descent (POD), TPFUS-derived parameters [bladder neck mobility (BNM), urethral rotation angle (URA), posterior vesicourethral angle (PVUA), levator ani muscle hiatus area (LAMHA)], and sEMG-related indices [Type I/II muscle fibers strength, dynamic vaginal pressure (DVP)]. The chi-square test was also used to assess the association between abnormal DVP and POD diagnosis.

The overall incidence of POD in the VD group (69.28%) was significantly higher than that in the CS group (43.86%, P < 0.05). The individual incidences of uterine prolapse and cystocele in the VD group were also significantly elevated compared with the CS group (all P < 0.05). Cystocele in both groups was predominantly classified as Green Type II, the individual incidences of rectocele and distribution of cystocele subtypes had no statistically significant difference between the two groups (P > 0.05). TPFUS measurements revealed that BNM, URA, PVUA, and LAMHA in the VD group were significantly larger than those in the CS group (all P < 0.001). Among these indicators, LAMHA yielded the largest t value, indicating the most substantial intergroup difference. sEMG results showed that the abnormal rates of the Type I and Type II muscle fibers had a significant intergroup difference (P < 0.001). The VD group had a higher incidence of abnormal DVP (66.01%) and a lower mean DVP value (78.72 ± 11.51 cmH₂O) compared with the CS group (both P < 0.001). Moreover, the chi-square test revealed a significant association between abnormal DVP and POD diagnosis (χ2 = 97.49, P < 0.001).

Combined examination with TPFUS and sEMG revealed that the VD group had a higher incidence of pelvic floor muscle abnormality, uterine prolapse, cystocele, abnormal type Ⅰ/Ⅱ muscle fibers and positive DVP findings compared with the CS group in the early postpartum period. Nevertheless, no significant differences were found between the two groups regarding the rectocele rate and cystocele classification. The combined use of TPFUS and sEMG allows comprehensive assessment of the pelvic floor from morphological and functional perspectives. LAMHA shows the most prominent between-group difference among all morphological indicators. As one key indicator, DVP serves as a reliable functional screening parameter. This joint evaluation can provide targeted guidance for early postpartum pelvic floor rehabilitation.