How does the type of delivery affect pelvic floor structure? MRI parameter-based anatomical study

The aim of this study is to examine the effects of delivery type and birth weight on pelvic floor structure using muscle defects, uterus-vagina angles and landmarks in pelvic magnetic resonance imaging (MRI).

This is a retrospective study. Pelvic MR images of 38 vaginal deliveries and 62 cesarean section patients who met the study criteria were analyzed. Pubococcygeal line, H line, M line were marked on MR images, uterus cervix, cervix upper vagina, upper and middle vagina, middle and lower vagina angles, urogenital hiatus width, levator hiatus width, obturator internus muscle area, levator ani defect was measured. The urinary incontinence and pelvic organ prolapse examination findings were recorded. The patients' age, body mass index (BMI), parity, delivery type, maximum birth weight questions were asked. The data of both groups were compared.

Uterocervical angle and levator ani muscle defect was significantly higher in the vaginal delivery group (p < 0.001). In the vaginal delivery group, a significant positive correlation was found between the parity and the levator ani muscle defect (r = 0.552), (p = 0.000). A significant negative correlation was found between the parity and the uterocervical angle (r = -0.337), (p = 0.039). A significant negative correlation was found between maximum birth weight and cervix upper vagina angle (r = -0.365) (p = 0.024). In the vaginal delivery group, a negative significant correlation was found between birth weight and obturator internus muscle area (r = -0.378), (p = 0.019).

These results show that cesarean section exposes the pelvic floor to less trauma and suggest that cesarean section may protect the pelvic floor.