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

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

Design: Cross sectional study and cohort study.

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

Participants: Cross sectional study: 7,557 women attending antenatal care. Cohort study: a subgroup of 1,726 pregnant women with one previous delivery at our department.

Results: The prevalence of anal incontinence within the preceding year was 8.6%. Incontinence of liquid and solid stools was reported in 2.3% and 0.6%, respectively. Isolated flatus incontinence at least once a week was reported in 4.2%. The risk of flatus incontinence at least once a week was increased with age > 35 years (OR 1.6; 95% CI 1.1-2.4) and with previous lower abdominal or urological surgery (OR 1.5, 95% CI 1-1-2.1) in a logistic regression model controlling for maternal factors. Increasing parity did not increase the risk. The risk of flatus incontinence was increased after anal sphincter tear and birthweight > 4,000 g in a logistic regression model controlling for maternal and obstetric variables. Episiotomy was insignificantly associated, while spontaneous perineal tear > 3 cm and a number of other intrapartum factors were not associated. CONCLUSION True faecal incontinence is rare among younger women. However, an age > 35 years and previous lower abdominal or urological surgery increased the risk of flatus incontinence in contrast to increasing parity. This suggests that childbirth plays a minor role compared with age. However, when analysing obstetric variables separately, a birthweight > 4,000 g, and anal sphincter tears were significant risk factors for flatus incontinence.