Urinary incontinence: prevalence and risk factors at 16 weeks of gestation.

Objective: To evaluate the prevalence of urinary incontinence at 16 weeks of gestation and to identify possible maternal and obstetric risk factors.

Design: Cross-sectional study and cohort study.

Setting: Department of Obstetrics and Gynaecology, Aarhus University Hospital, Denmark.

Population: Cross-sectional study: 7795 women attending antenatal care. Cohort study: a sub-group of 1781 pregnant women with one previous delivery at our department.

Results: Prevalence and maternal risk factors: the prevalence of urinary incontinence within the preceding year was 8.9% among women at 16 weeks of gestation (nulliparae, 3.9%, para 1, 13.8%, para 2+, 16.2%). Stress or mixed incontinence occurred at least weekly in 3% of all the women. After adjusting for age, parity, body mass index, smoking, previous abortions, and previous lower abdominal or urological surgery in a logistic regression model, primiparous women who had delivered vaginally had higher risk of stress or mixed urinary incontinence than nulliparous women (OR 5.7; 95% CI 3.9-8.3). Subsequent vaginal deliveries did not increase the risk significantly. Young age, body mass index > 30, and smoking were possible risk factors for developing urinary incontinence. Obstetric factors: weight of the newborn > 4000 g (OR 1.9; 95% CI 1.0-3.6) increased the risk of urinary incontinence; mediolateral episiotomy in combination with birthweight > 4000 g also increased the risk (OR 3.5; 95% CI 1.2-10.2); a number of other intrapartum factors did not increase the risk of urinary incontinence.

Conclusions: The first vaginal delivery was a major risk factor for developing urinary incontinence; subsequent vaginal deliveries did not increase the risk significantly. Birthweight > 4000 g increased the risk; episiotomy in combination with birthweight > 4000 g also increased the risk.