Objective: This study aimed to investigate pelvic floor biometry of asymptomatic primiparous women compared with nulliparous women by using four-dimensional transperineal ultrasound (4D TPUS).
Methods: From July 2015 to February 2017, 722 women were enrolled and divided into the nulliparous group (n = 292), the vaginal delivery group (n = 272), and the elective cesarean section group (n = 158). The ultrasound parameters of 4D TPUS were compared among the groups.
Results: The vaginal delivery group had a significantly greater bladder neck descent (η2 = 0.04), retrovesical angles on Valsalva maneuver (η2 = 0.01), urethral rotation (η2 = 0.01), levator hiatus area on Valsalva maneuver (η2 = 0.02), urethral inclination angle (η2 = 0.02), and funneling of the proximal urethra (η2 = 0.11) than the other two groups. Comparison of the two modes of delivery (vaginal delivery and cesarean section) also showed significant differences in the above-mentioned ultrasound parameters.
Conclusion: There are significant differences in pelvic floor biometry between asymptomatic primiparous women and nulliparous women, as well as between women with vaginal delivery and those with elective cesarean section.
Keywords: Vaginal delivery; Valsalva maneuver; bladder neck descent; cesarean section; four-dimensional ultrasound; nulliparous; pelvic floor; primiparous.