Longitudinal Changes in the Genital Hiatus Preceding the Development of Pelvic Organ Prolapse

Abstract

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.

Figure 1

Size of the genital hiatus (GH) at study entry (A) and 5-year change in GH (B), Mothers’ Outcomes After Delivery Study, 2008–2018. The graph shows empirical Bayes estimates based on the univariable model presented in Table 2. Each point depicts the pairing of the estimate for the case (y-axis) with the median of the estimates for that case’s matched controls (x-axis).