Genital Hiatus Size and the Development of Prolapse Among Parous Women.

OBJECTIVE: In cross-sectional studies, pelvic organ prolapse is strongly associated with genital hiatus (GH) size. The objective of this study was to estimate prolapse incidence by the size of the GH among parous women followed prospectively. METHODS: Data were derived from a longitudinal study of pelvic floor disorders. Participants were followed annually for 2-9 years. Genital hiatus size and prolapse beyond the hymen were assessed with annual pelvic organ prolapse quantification examinations. Kaplan-Meier methods described prolapse-free survival as a function of GH size. Accounting for changes over time in GH size, lognormal models were used to estimate prolapse-free survival by GH size. This analysis was repeated separately for women who gave birth exclusively by cesarean versus those with at least one vaginal birth. RESULTS: Among 1,492 participants, median age at enrollment was 38 years; 153 (10.3%) developed prolapse over 2-9 years. The cumulative probability of prolapse increased substantially as the size of the GH increased. Lognormal models predicted that the estimated median time to develop prolapse would be 33.4 years for women with a persistent GH of 3 cm; in contrast, the estimated median time to develop prolapse would be 5.8 years for a GH of 4.5 cm or greater. Considering separately women who gave birth by cesarean versus those with at least 1 vaginal birth, GH size drastically modified prolapse risk in both birth groups. CONCLUSIONS: Prolapse incidence is strongly associated with GH size, regardless of delivery mode. These findings suggest that a wider GH is an important predictor of future prolapse risk.