Delivery mode is a major environmental determinant of stress urinary incontinence: Results of the Evanston-Northwestern Twin Sisters Study

Objective: We Studied a large cohort of identical twin sisters, utilizing the unique properties of a twin research design to explore the relationship between obstetrical delivery mode and stress urinary incontinence. Study design: An anonymous 67-item survey was completed by 271 identical twin pairs (n = 542) at the world's largest annual gathering of twins. Logistic regression for repeated binary measures was used to evaluate risk factors and accounting for shared genetics within pairs. Results: The twins had a mean age of 47.1 years (range 15 to 85 years), and stress urinary incontinence was reported by 51.8%. Stress urinary incontinence was associated with age (P = .001), parity (P = .001), obesity (P = .002), and birth mode, with vaginal delivery conferring a considerable increase in stress urinary incontinence risk relative to cesarean section (odds ratio 2.28, 95% confidence interval 1.14 to 4.55, P =.019). Conclusion: Vaginal delivery mode represents a potent determinant of stress urinary incontinence, carrying more than twice the risk of cesarean section. This study of identical twins provides new insight into the epidemiology of female incontinence. (c) 2005 Mosby, Inc. All rights reserved.