Background: Approximately 10 percent of women in the United States undergo surgery for pelvic organ prolapse, and almost 30 percent of these women require additional treatment for recurrence. Traditionally, vaginal delivery has been regarded as the most significant risk factor for later development of pelvic prolapse. This association has been challenged because most parous women never develop prolapse and because the condition has been observed in nulliparous women.
Other factors that have been implicated include white race, high body mass index (BMI), older age, smoking, constipation, and vaginal hysterectomy. An increased risk also has been identified in female relatives of patients with advanced prolapse. Buchsbaum and colleagues studied pairs of sisters to investigate the roles of vaginal delivery and familial factors in pelvic organ prolapse.
The Study: The authors used data from a large population study of gynecologic conditions to identify 101 pairs of postmenopausal sisters in which one sister was nulliparous and the other had at least one vaginal delivery. Participants completed extensive questionnaires to provide data on medical, surgical, obstetric, and medication history, as well as symptoms of pelvic organ prolapse (e.g., urinary or fecal incontinence, pelvic pressure or bulging). Demographic data also were collected.
All participants received a physical examination, including analysis of gait, mobility, and pelvic relaxation, and general pelvic and rectal examination. Sisters were scheduled to be evaluated on different days, and the examiners were blinded to sibling and parity status. All assessments used standardized scales to document findings. The primary outcomes of interest were urinary incontinence and pelvic organ prolapse of stage II or greater.
Results: The nulliparous women did not differ from the parous women in any significant variable. For both groups, the mean age was 60 years and the mean BMI was 28 kg per m2. Hysterectomy was reported in 27 percent of parous women and in 24 percent of nulliparous women. Ten of the nulliparous women and 24 of the parous women reported previous vaginal surgery. The average parity for the parous women was three.
There was no pelvic organ prolapse in 82.2 percent of the nulliparous women and in 43.6 percent of the parous women. Nevertheless, a statistically significant familial association was observed. The concordance in prolapse stage between sisters ranged from 74.3 percent for the anterior compartment to 91.1 percent for the apical compartment. In the 25 pairs of sisters with discordant findings, the prolapse was more advanced in the parous sister in all but three pairs.
Measures of pelvic support showed that at least two thirds of the sister pairs had similar measurements (within 1 cm) except at the cervix or vaginal cuff. In the remaining one third of pairs, the parous sister had greater descent in 80 percent of cases. Statistical analysis showed a twofold increase in risk of posterior wall prolapse and a threefold increase in risk of anterior wall prolapse with each vaginal birth. Other factors, including BMI, were not associated with risk of prolapse.
Conclusion: The authors conclude that familial factors are highly significant in the development of pelvic organ prolapse. Parity appears to confer a small additional risk of severe prolapse.