BACKGROUND: The aims of the present study were to describe the prevalence of stress incontinence, as described by women themselves, 1 year after childbirth in a national sample of Swedish-speaking women, and to identify possible predictors. METHODS: A cohort study, including 2390 women recruited from 593 antenatal clinics in Sweden during three 1-week periods evenly spread over 1 year (1999-2000), representing 53% of women eligible for the study and 75% of those who consented to participate. Data were collected by means of questionnaires in early pregnancy, 2 months and 1 year after the birth, and from the Swedish Medical Birth Register. RESULTS: One year after the birth, 22% of the women had symptoms of stress incontinence but only 2% said it caused them major problems. The strongest predictor was urinary incontinence (overall leakage) 4-8 weeks after a vaginal delivery (OR 5.5, CI 95% 4.1-7.4) as well as after a cesarean section (OR 11.9, CI 95% 2.9-48.1). Other predictors in women with a vaginal delivery were: multiparity (OR 1.4; CI 95% 1.1-1.8), obesity (OR 1.6; CI 95% 1.1-2.4) and constipation 4-8 weeks postpartum (OR 1.4; CI 95% 1.1-1.9). CONCLUSION: Stress incontinence 1 year after childbirth is a common symptom, which could possibly be reduced by identifying women with urinary leakage at the postnatal check-up.