To investigate the prevalence and risk factors for urinary incontinence (UI) 20 years after one vaginal delivery or one caesarean section.
Registry-based national cohort study.
Women who returned postal questionnaires (response rate 65.2%) in 2008.
Singleton primiparae who delivered in the period 1985-1988 with no further births (n = 5236).
The Swedish Pregnancy, Obesity and Pelvic Floor (SWEPOP) study linked Medical Birth Register (MBR) data to a questionnaire about UI.
Prevalence of UI and UI for more than 10 years (UI > 10 years) were assessed 20 years after childbirth.
The prevalence of UI (40.3 versus 28.8%; OR 1.67; 95% CI 1.45-1.92) and UI > 10 years (10.1 versus 3.9%; OR 2.75; 95% CI 2.02-3.75) was higher in women after vaginal delivery than after caesarean section. There was no difference in the prevalence of UI or UI > 10 years after an acute caesarean section or an elective caesarean section. We found an 8% increased risk of UI per current body mass index (BMI) unit, and age at delivery increased the UI risk by 3% annually.
Two decades after one birth, vaginal delivery was associated with a 67% increased risk of UI, and UI > 10 years increased by 275% compared with caesarean section. Our data indicate that it is necessary to perform eight or nine caesarean sections to avoid one case of UI. Weight control is an important prophylactic measure to reduce UI. Current BMI was the most important BMI-determinant for UI, which is important, as BMI is modifiable.