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: 7557 women attending antenatal care. Cohort study: a subgroup of 1726 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 > 4000 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 > 4000 g, and anal sphincter tears were significant risk factors for flatus incontinence.