Symptomatic pelvic organ prolapse in middle-aged women: a national matched cohort study on the influence of childbirth.

Background: The relative impact of age, pregnancy, and vaginal delivery on symptomatic pelvic organ prolapse is still an unresolved issue that involves the controversial question about the protective effect of cesarean section.

Objective: The purpose of this study was to compare the age-related prevalence of symptomatic genital prolapse in nulliparous, vaginal- and cesarean-delivered women aged 40-64 years.

Study Design: This Swedish, nationwide matched cohort study involved 14,335 women. Three restricted, randomly selected source cohorts of women (nulliparous women unexposed to childbirth [n = 9136], 1-para cesarean delivered women, exposed to 1 pregnancy [n = 1412], and 1-para women exposed to 1 pregnancy followed by vaginal delivery [n = 3787]) were retrieved from the Swedish Medical Birth Register and Statistics Sweden and surveyed in 2008 and 2014. The surveys used a postal and Internet-based questionnaire containing validated questions for pelvic floor disorders. Symptomatic prolapse was defined by the question, "Do you have a sensation of tissue protrusion (a vaginal bulge) from your vagina?" In this study the symptom frequencies, sometimes and often, were defined as a positive response. Parous women were all assessed 20 years postnatally. One-to-one matching with an age interval for pairing of 3 years and 3 units of body mass index (kilograms per square meter) was used in women aged 40-64 years. The procedure succeeded in 2635 of 2640 women (99.8%), resulting in an adequate distribution of age and body mass index (kilograms per square meter) between matched groups. For comparison between groups, a Fisher exact test was used for categorical variables and the Mann-Whitney U test for continuous variables. Trend between matched groups was analyzed with Mantel-Haenszel statistics. Estimated, age-related values of symptomatic prolapse were obtained by logistic regression analysis.

Results: In nulliparous and cesarean-delivered women, the prevalence of symptomatic prolapse was relatively similar and below 5% across ages 40-64 years. In contrast, in women after vaginal delivery, there was an accelerating increase in the prevalence of symptomatic genital prolapse up to 65 years of age. Estimated probability from the regression model increased 4-fold, from 3.8% at 40 years to 13.4% at 64 years of age. The observed induction period associated with 1 vaginal delivery seemed to be at least 20 years among women giving birth in their early 20s. At age 64 years, the estimated probability of symptomatic prolapse was 12 times higher after vaginal delivery compared with cesarean deliery (13.4% [95% confidence interval, 9.4-18.9] vs 1.1% [95% confidence interval, 0.4-2.5], P < .0001). The calculated reduction of symptomatic prolapse by cesarean delivery at 64 years of age was thus 92%.

Conclusion: In this national matched cohort study, the interaction between vaginal delivery and aging was the most important factor for the occurrence of symptomatic prolapse. Because the effect of aging can be modified only to a small extent, preventive strategies for genital prolapse should focus on how to avoid the adverse events related to a vaginal delivery.