Background: Approximately one in every nine U.S. women undergoes surgery for conditions associated with pelvic prolapse, but little is understood about the natural history of the condition or factors that might exacerbate or slow its progression.

The Study: Bradley and colleagues asked participants in one center of the Women's Health Initiative (WHI) Hormone Therapy clinical trial to volunteer for a longitudinal observational study of the natural progression of pelvic organ prolapse. Participants had to be postmenopausal and have an intact uterus. The study followed 259 women for one to three years. The average age of participants was 68 years, the mean body mass index (BMI) was 30.1 kg per m², and the median number of vaginal births was four (ranging from zero to 12). Only 21 (8.1 percent) were current smokers. About one half (45.6 percent) had been assigned to the placebo arm of the WHI study, and 141 women had been assigned to take estrogen and progesterone.

The women were examined every year using the pelvic organ prolapse quantification system, a validated method of documenting prolapse findings on pelvic examination. All examinations followed the same protocol and were performed by trained research nurses. Data were also collected on variables related to pelvic prolapse such as BMI, vaginal parity, smoking, waist circumference, and education level.

Results: The incidence and degree of clinically recognized prolapse varied over time in individual women. The overall incidences for years 1 and 3 were 26 and 40 percent, respectively. Conversely, rates of prolapse resolution for the same years were 21 and 19 percent. Over three years, the maximal vaginal descent increased by 0.8 inches (2 cm) or more in 11 percent of women but decreased by the same amount in 2.7 percent. The risk of progression was related to increased BMI, waist circumference of 31.5 inches (80 cm) or more, and a history of five or more vaginal deliveries. Smoking was associated with a decreased risk of descent, but this association was not found when researchers controlled for BMI. Assignment to treatment with hormones did not influence the risk of descent.

Conclusion: The authors conclude that vaginal descent is common in postmenopausal women, but that the rate of progression is variable and the condition can regress. Only one in 10 women had descent of 2 cm or more, and the risk of descent was related to obesity and a history of at least five vaginal births. Clinically significant progression over the three-year study was rare. The authors believe that women with evidence of vaginal descent can be reassured that they are at low risk of significant progression over three years.