The likelihood of vaginal descent progression and regression of at least 2 cm similarly depended on the baseline level of vaginal descent (data not shown). Overall, a 1-year progression (increase) in maximal vaginal descent by 2 cm or greater occurred in 5.8% (95% CI 3.2–9.6%) of the women and a 1-year regression (decrease) of 2 cm or greater occurred in 1.2% (95% CI 0.26–3.6%). Over 3 years, the maximal vaginal descent increased by 2 cm or greater in 11.0% (95% CI 4.9–20.5%) of the women and decreased by 2 cm or greater in 2.7% (95% CI 0.3–9.5%).
Risk factors associated with any increase and any decrease in the maximal vaginal descent are presented in Table 2. Increasing BMI and grand multiparity (five or more vaginal deliveries) increased the risk for vaginal descent progression. Current smokers had an independent decreased risk for vaginal descent progression in the model, but smokers had a lower mean BMI than nonsmokers (26.2 versus 30.5 kg/m2; P=.002).
In a separate model, increasing BMI and parity were inversely associated with vaginal descent regression. Randomization assignment to estrogen-progesterone treatment compared with placebo was not associated with changes in vaginal descent. A post hoc power calculation using our actual sample size and the observed 1-year vaginal descent progression rate in the women assigned to the placebo group (34.5%) suggests that our sample size provided 80% power at a 5% significance level to identify an increase or decrease of at least 19 percentage points in this rate in the estrogen-progesterone group compared with the placebo group.
Based on this study’s findings, mild POP is a fluid state. On balance, older parous women are more likely to develop new or progressive prolapse than to regress, but the “net” annual change in vaginal descent (progression rate – regression rate), is much lower than the overall progression rate. Risk factors for maximal vaginal descent progression include the baseline level of vaginal descent, as well as BMI, waist circumference, and vaginal parity. In this group of women, smoking was protective against increasing vaginal descent. However, given the association between smoking and BMI, smoking may be a proxy for lower BMI as opposed to having a true protective effect.
When initially designing this study, we did not consider the possibility that prolapse could resolve. During the course of the study, Handa et al10 reported intriguing results from women enrolled at a different Women’s Health Initiative site: annual regression rates for prolapse exceeded progression rates. However, prolapse was not assessed using a validated or quantitative tool, but rather using the larger Women’s Health Initiative trial examination technique in which the vagina was visualized during straining without a speculum in place. Given this less rigorous method of assessing prolapse, some considered these findings a result of measurement error. Our results, using a standardized, quantitative, and reproducible method of assessing prolapse confirm that early POP does indeed wax and wane. However, contrary to Handa’s findings, progression of prolapse was more likely in our study than regression.
On the other hand, alternative conclusions from our results must also be considered. The vaginal descent “progression” and “regression” observed in these women could represent variability in vaginal descent. The time of examination, exact bladder volume, and Valsalva efforts during examination were not standardized and might impact observable levels of vaginal descent or prolapse. In addition, although the POP-Q examination tool has proven reproducibility, no tool is perfect, and our results might also result in part from variability inherent in POP-Q measurements. To partially offset such limitations, we studied progression and regression of descent in terms of 2-cm or greater changes in addition to 1-cm changes.
We evaluated changes in pelvic support by describing both how vaginal descent changed from year to year using the continuous variable of maximal vaginal descent and how women changed back and forth from having prolapse (defined dichotomously as present when the maximal vaginal descent was at or beyond the hymen). Although the initial POP-Q report defined prolapse as present when the POP-Q stage was I or greater, this definition would classify 98% of our subjects as having prolapse at baseline, precluding a meaningful comparison of women with and without prolapse.4 We chose to use the hymeneal ring as the cut point for a dichotomous definition of prolapse because women with descent at or below this level are more likely to report seeing or feeling a vaginal bulge than are women with less vaginal descent, and researchers increasingly suggest this demarcation to define prolapse.8,11,12
Women in this study were of a similar age to women most likely to undergo surgery for prolapse, and therefore we believed this to be an ideal age at which to study the natural history of POP.13 Each of our participants had a uterus. We chose to study this group to understand the natural history of pelvic support in women without detachment of the apical vaginal support structures, and women who have had hysterectomy are more likely to have had prior prolapse surgery. Our findings cannot be generalized to younger women or to those without a uterus.
In conclusion, we suggest that vaginal descent occurring within the vagina is common in older, parous women, and that the point of maximal vaginal descent (as measured by the POP-Q system) may decrease, as well as increase, over time. In fact, we found that women with minimal vaginal descent at baseline are more likely to progress in future examinations and women with more descent, to regress, over time. This finding is perhaps intuitive because each has more potential movement in the opposite direction, but this has not been previously reported. This finding is also suggestive of the well-known phenomenon of regression to the mean. This principle states that, of related measurements, where first measurement is higher or lower relative to the mean, the expected value of the second measurement will be closer to the mean than to the observed value of the first measurement.14
Overall, clinically significant progression of vaginal descent was uncommon in this group over a 3-year period in that only one woman underwent surgery for this reason and four reported pessary use. One in 10 women demonstrated 2-cm or greater progression in maximal vaginal descent, a potentially significant anatomic change. The number of women who regressed by this amount was much smaller (2.7%). Even longer follow-up and larger numbers of women will be needed to identify women as they transition from having early, largely asymptomatic prolapse to having bothersome bulges. Our data suggest that clinicians can reassure women with vaginal descent within the vagina that their chance of significant progression over a 1- to 3-year period is low.
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3. Swift SE. The distribution of pelvic organ support in a population of female subjects seen for routine gynecologic health care. Am J Obstet Gynecol 2000;183:277–85.
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APPENDIX: SHORT LIST OF WOMEN’S HEALTH INITIATIVE INVESTIGATORS
Program Office: (National Heart, Lung, and Blood Institute, Bethesda, MD) Barbara Alving, Jacques Rossouw, Shari Ludlam, Linda Pottern, Joan McGowan, Leslie Ford, and Nancy Geller.
Clinical Coordinating Center: (Fred Hutchinson Cancer Research Center, Seattle, WA) Ross Prentice, Garnet Anderson, Andrea LaCroix, Charles L. Kooperberg, Ruth E. Patterson, Anne McTiernan; (Wake Forest University School of Medicine, Winston-Salem, NC) Sally Shumaker; (Medical Research Labs, Highland Heights, KY) Evan Stein; (University of California at San Francisco, San Francisco, CA) Steven Cummings.
Clinical Centers: (Albert Einstein College of Medicine, Bronx, NY) Sylvia Wassertheil-Smoller; (Baylor College of Medicine, Houston, TX) Jennifer Hays; (Brigham and Women’s Hospital, Harvard Medical School, Boston, MA) JoAnn Manson; (Brown University, Providence, RI) Annlouise R. Assaf; (Emory University, Atlanta, GA) Lawrence Phillips; (Fred Hutchinson Cancer Research Center, Seattle, WA) Shirley Beresford; (George Washington University Medical Center, WA, DC) Judith Hsia; (Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA) Rowan Chlebowski; (Kaiser Permanente Center for Health Research, Portland, OR) Evelyn Whitlock; (Kaiser Permanente Division of Research, Oakland, CA) Bette Caan; (Medical College of Wisconsin, Milwaukee, WI) Jane Morley Kotchen; (MedStar Research Institute/Howard University, WA, DC) Barbara V. Howard; (Northwestern University, Chicago/Evanston, IL) Linda Van Horn; (Rush Medical Center, Chicago, IL) Henry Black; (Stanford Prevention Research Center, Stanford, CA) Marcia L. Stefanick; (State University of New York at Stony Brook, Stony Brook, NY) Dorothy Lane; (The Ohio State University, Columbus, OH) Rebecca Jackson; (University of Alabama at Birmingham, Birmingham, AL) Cora E. Lewis; (University of Arizona, Tucson/Phoenix, AZ) Tamsen Bassford; (University at Buffalo, Buffalo, NY) Jean Wactawski-Wende; (University of California at Davis, Sacramento, CA) John Robbins; (University of California at Irvine, CA) F. Allan Hubbell; (University of California at Los Angeles, Los Angeles, CA) Howard Judd; (University of California at San Diego, LaJolla/Chula Vista, CA) Robert D. Langer; (University of Cincinnati, Cincinnati, OH) Margery Gass; (University of Florida, Gainesville/Jacksonville, FL) Marian Limacher; (University of Hawaii, Honolulu, HI) David Curb; (University of Iowa, IA/Davenport, IA) Robert Wallace; (University of Massachusetts/Fallon Clinic, Worcester, MA) Judith Ockene; (University of Medicine and Dentistry of New Jersey, Newark, NJ) Norman Lasser; (University of Miami, Miami, FL) Mary Jo O’Sullivan; (University of Minnesota, Minneapolis, MN) Karen Margolis; (University of Nevada, Reno, NV) Robert Brunner; (University of North Carolina, Chapel Hill, NC) Gerardo Heiss; (University of Pittsburgh, Pittsburgh, PA) Lewis Kuller; (University of Tennessee, Memphis, TN) Karen C. Johnson; (University of Texas Health Science Center, San Antonio, TX) Robert Brzyski; (University of Wisconsin, Madison, WI) Gloria E. Sarto; (Wake Forest University School of Medicine, Winston-Salem, NC) Denise Bonds; (Wayne State University School of Medicine/Hutzel Hospital, Detroit, MI) Susan Hendrix.