Selective estrogen receptor modulators (SERMs) were developed for the treatment and prevention of osteoporosis in postmenopausal women. These agents provide the positive benefits of hormone replacement on bone and cardiovascular systems. Several clinical trials have reported neutral or antiestrogenic effects on the uterus, and cases of pelvic floor relaxation and uterine prolapse associated with SERM use have been reported. Goldstein and colleagues examined data from several studies to determine if SERM use was associated with an increased risk of surgery for pelvic organ prolapse and urinary incontinence.

They analyzed data from three randomized, placebo-controlled trials of raloxifene in the prevention of osteoporosis. These trials included 4,680 women treated with raloxifene and 2,246 control subjects, all with intact uteri. The majority of these participants had undergone transvaginal ultrasonographic examination. Data were gathered on procedures performed for pelvic organ prolapse, urinary incontinence, or hysterectomy for up to three years after the trials.

The two groups of women were comparable at baseline and reported similar low incidence (7.3 to 8.4 percent) of urinary incontinence or pelvic organ prolapse. The average age of the participants was about 65 years, most were 15 years postmenopausal, and the groups were similar in rates of use of alcohol, tobacco, and hormone replacement therapy. In the placebo group, 34 (1.51 percent) women had surgery for pelvic floor relaxation, compared with 35 (0.75 percent) women treated with raloxifene. The authors calculate the adjusted odds ratio to be 0.5, indicating that raloxifene was associated with about a 50 percent reduction in the risk of pelvic floor surgery. The benefit appeared stronger in older women and became apparent after about nine months of therapy.

The authors conclude that raloxifene does not increase pelvic floor relaxation. Conversely, SERMs may have a protective effect against uterine prolapse and urinary incontinence. A positive effect on collagen metabolism may explain this apparent effect.