Comparative magnetic resonance imaging-based study of pelvic floor morphology and function before pregnancy and after primigravida vaginal delivery

Background: Vaginal childbirth is one of the main risk factors for pelvic floor dysfunction. Magnetic resonance imaging (MRI) can facilitate quantitative evaluation of the morphology and function of the pelvic floor in static and dynamic environments. The objective of this study was to investigate the changes in pelvic floor morphology and function in primigravida women before pregnancy (BP) and after vaginal delivery.

Methods: Primigravida women underwent pelvic floor MRI scans BP, at 3 months postpartum (3mPP), and at 6 months postpartum (6mPP). Various pelvic floor MRI data were measured, including the obturator internus muscle (OIM) area, anterior pelvic area, puborectalis muscle thickness (PRT), levator plate angle (LPA), iliococcygeal angle, bladder-pubococcygeal line (B-PCL), uterus-pubococcygeal line (U-PCL), puborectal hiatus line, muscular pelvic floor relaxation line, levator hiatus area, urethral mobility, bladder neck descent, and cervix descent.

Results: In the resting state, the OIM area and PRT decreased whereas the anterior pelvic area increased from BP to 3mPP. During the straining maneuver, all parameters except U-PCL and urethral mobility showed statistically significant differences (P < 0.05). The OIM area and PRT increased whereas the anterior pelvic area decreased from 3mPP to 6mPP. During the straining maneuver, B-PCL, bladder neck descent, levator hiatus area, and LPA showed statistically significant differences (P < 0.05). In the resting state, the OIM area and PRT decreased whereas the anterior pelvic area increased from BP to 6mPP. During the straining maneuver, B-PCL, muscular pelvic floor relaxation line, and bladder neck descent showed statistically significant differences (P < 0.05).

Conclusion: Vaginal delivery can cause pelvic floor injury that may gradually recover over time. However, the injury does not fully recover to the pre-pregnancy level within 6mPP.