Does pregnancy affect pelvic floor functional anatomy? A retrospective study

OBJECTIVE: Vaginal childbirth is an established main aetiological factor in the pathogenesis of female pelvic floor dysfunction. However, pregnancy itself is also likely to have an effect. This study investigated the effect of pregnancy on pelvic floor functional anatomy.

STUDY DESIGN: This was a retrospective observational study involving vaginally nulliparous women who presented to a tertiary urogynaecology unit with symptoms and signs of pelvic floor dysfunction between 2006 and 2014. Nulliparous women were compared with those who delivered exclusively by Caesarean Section (CS). All had undergone a standardised clinical interview, ICS POP-Q assessment and 3D/4D translabial pelvic floor ultrasound. Main outcome measures included sonographically determined pelvic organ position and hiatal dimensions on Valsalva and pelvic floor muscle contraction (PFMC).

RESULTS: Of 2930 women seen during the study period, 242 had never given birth vaginally. One hundred and twenty-nine (53 %) were nulliparous, and 113 (47 %) were delivered by CS only. The CS group demonstrated significantly higher pelvic organ mobility in the anterior compartment (all P < 0.05) and a larger hiatal area on Valsalva (P = 0.004). All sonographic measures of pelvic floor muscle function demonstrated greater tissue displacement on PFMC in the CS group (all P < 0.05).

CONCLUSIONS: Compared to nulliparas, women who delivered exclusively by CS showed increased pelvic organ descent on Valsalva and tissue displacement on PFMC, implying increased tissue elasticity/ compliance or reduced stiffness, consistent with a small permanent hormonal and/or mechanical effect of pregnancy.