Female Pelvic Floor Organ Prolapse

The human female pelvis evolved as a balance between the requirements of both bipedal ambulation and parturition. In quadrupeds the abdominal organs are held in place by the abdominal wall, whereas in bipeds the pelvic floor sustains them. The change in ambulation resulted in anatomical changes to the pelvic shape, angle, and pelvic musculature, such as the transition of muscles once used to support a tail to part of the pelvic floor. However, these adaptive changes also make human females more susceptible to genital prolapse.

Genital prolapse is where pelvic floor collapse results in part of the vaginal canal to protrude from the opening of the vagina. This is a consequence of damage to the endopelvic tissue from vaginal delivery, combined with risk factors including larger pelvis and pelvic floors, and increased abdominal pressure from circumstances such as obesity or chronic lung conditions. Fossil evidence from Australopithecus shows pelvic changes consistent with upright walking as compared to the great apes. Australopithecus had a narrower pelvis than modern humans likely resulting in complex obstetrical mechanics for childbirth. Modern human pelvic size and angle results in easier parturition but increases the risk of genital prolapse as compared to either the great apes or Australopithecus.