We aimed to explore relationships between changes in genital hiatus (GH) and development of pelvic organ prolapse using data from the Mothers' Outcomes After Delivery (MOAD) Study, a Baltimore, Maryland, cohort study of parous women who underwent annual assessments during 2008-2018. Prolapse was defined as any vaginal segment protrusion beyond the hymen or reported prolapse surgery. For each case, 5 controls (matched on birth type and interval from first delivery to study enrollment) were selected using incidence sampling methods. We used a mixed model whose fixed effects described the initial size and slope of the GH as a function of prolapse status (case vs. control) and with nested (women within matched sets) random effects. Among 1,198 women followed for 1.0-7.3 years, 153 (13%) developed prolapse; 754 controls were matched to those women, yielding 3,664 visits for analysis. GH was 20% larger among the cases at enrollment (3.16 cm in cases vs. 2.62 cm in controls; P < 0.001), and the mean rate of increase in the size of the GH was more than 3 times greater (0.56 cm per 5-year period vs. 0.15 cm per 5-year period in controls; P < 0.001). Thus, to identify women at highest risk for developing prolapse, health-care providers could evaluate not simply the size of the GH but also changes in the GH over time.
Keywords: empirical Bayes methods; genital hiatus; mixed-effects models; nested case-control studies; pelvic organ prolapse.
© The Author(s) 2019. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health.