New postnatal urinary incontinence: obstetric and other risk factors in primiparae

Objectives To identify obstetric and other risk factors for urinary incontinence that occurs during pregnancy or after childbirth. Design Questionnaire survey of women. Setting Maternity units in Aberdeen (Scotland), Birmingham (England) and Dunedin (New Zealand). Population A total of 3405 primiparous women with singleton births delivered during 1 year. Methods Questionnaire responses and obstetric case note data were analysed using multivariate analysis to identify associations with urinary incontinence. Main Outcome measures Urinary incontinence at 3 months after delivery first starting in pregnancy or after birth. Results The prevalence of urinary incontinence was 29%. New incontinence first beginning after delivery was associated with older maternal age (oldest versus youngest group, OR 2.02, 95% CI 1.35-3.02) and method of delivery (caesarean section versus spontaneous vaginal delivery, OR 0.28, 95% CI 0.19-0.41). There were no significant associations with forceps delivery (OR 1.18, 95% CI 0.92-1.51) or vacuum delivery (OR 1.16, 95% CI 0.83-1.63). Incontinence first occurring during pregnancy and still present at 3 months was associated with higher maternal body mass index (BMI > 25, OR 1.68, 95% CI 1.16-2.43) and heavier babies (birthweight in top quartile, OR 1.56, 95% CI 1.12-2.19). In these women, caesarean section was associated with less incontinence (OR 0.39, 95% CI 0.27-0.58) but incontinence was not associated with age. Conclusions Women have less urinary incontinence after a first delivery by caesarean section whether or not that first starts during pregnancy. Older maternal age was associated with new postnatal incontinence, and higher BMI and heavier babies with incontinence first starting during pregnancy. The effect of further deliveries may modify these findings.