Pelvic Organ Prolapse (POP) is a major clinical burden affecting 25% of women, with vaginal delivery a major contributing factor. We hypothesised that increasing parity weakens the vagina by altering the extracellular matrix proteins and smooth muscle thereby leading to POP vulnerability. We used a modified POP-quantification (POP-Q) system and a novel pressure sensor to measure vaginal wall weakness in nulliparous, primiparous and multiparous ewes. These measurements were correlated with histological, biochemical and biomechanical properties of the ovine vagina. Primiparous and multiparous ewes had greater displacement of vaginal tissue compared to nulliparous at points Aa, Ap and Ba and lower pressure sensor measurements at points equivalent to Ap and Ba. Vaginal wall muscularis of multiparous ewes was thinner than nulliparous and had greater elastic fibre content. Collagen content was lower in primiparous than nulliparous ewes, but collagen organisation did not differ. Biomechanically, multiparous vaginal tissue was weaker and less stiff than nulliparous. Parity had a significant impact on the structure and function of the ovine vaginal wall, as the multiparous vaginal wall was weaker and had a thinner muscularis than nulliparous ewes. This correlated with “POP-Q” and pressure sensor measurements showing greater tissue laxity in multiparous compared to nulliparous ewes.

A modified POP-Q in conscious ewes was established showing that the vaginal wall of parous animals has similar regions of weakness as do women and may be similarly related to parity. Ewes appear to be a representative preclinical model of human vaginal prolapse.

In this observational study, we found a strong association between all tested measures of posterior compartment descent and BMI, both clinical and on imaging.

Pelvic organ prolapse (POP) occurs when changes to the pelvic organ support structures cause descent or herniation of the pelvic organs into the vagina. Clinical evaluation of POP is a series of manual measurements known as the pelvic organ prolapse quantification (POP-Q) score. However, it fails to identify the mechanism causing POP and relies on the skills of the practitioner. We report on a modified vaginal speculum incorporating a double-helix fiber-Bragg grating structure for distributed pressure measurements along the length of the vagina and include preliminary data in an ovine model of prolapse. Vaginal pressure profiles were recorded at 10 Hz as the speculum was dilated incrementally up to 20 mm. At 10-mm dilation, nulliparous sheep showed higher mean pressures ( 102 ± 46 ?? mmHg ) than parous sheep ( 39 ± 23 ?? mmHg ) ( P = 0.02 ), attributable largely to the proximal (cervical) end of the vagina. In addition to overall pressure variations, we observed a difference in the distribution of pressure that related to POP-Q measurements adapted for the ovine anatomy, showing increased tissue laxity in the upper anterior vagina for parous ewes. We demonstrate the utility of the fiber-optic instrumented speculum for rapid distributed measurement of vaginal support.