Symptoms of fecal incontinence two decades after no, one, or two obstetrical anal sphincter injuries.

Background: The long-term effects of 1 or 2 consecutive obstetrical anal sphincter injuries on bowel continence are still inadequately investigated, and published results remain contradictory.

Objective: This study aimed to present detailed descriptive measures of the current bowel incontinence 20 years after the first birth in women who had 2 vaginal deliveries with and without sphincter injuries.

Study Design: Birth register data were used prospectively and linked to information from a questionnaire survey about current symptoms. Women with 2 singleton vaginal births, from 1992 to 1998, and no further births were retrieved and surveyed by the Swedish Medical Birth Register and Statistics Sweden in 2015. A simple random sample of 11,000 women was drawn from a source cohort of 64,687 women. The cumulative effect was studied in all women with a repeat sphincter injury from 1987 to 2000. Postal and web-based questionnaires were used. The study population consisted of 6760 women with no sphincter injury, 357 with 1 sphincter injury, and 324 women with 2 sphincter injuries. Women with 2 deliveries without sphincter injuries aged 40 to 60 years as reference, were compared with those of women that sustained 1 or 2 consecutive sphincter injuries. Here, third- and fourth-degree perineal tears were presented as 1 group. Fecal incontinence was defined as current involuntary leakage of solid or liquid stool, with and without concomitant leakage of gas. The Fisher exact test and the Mann-Whitney U test were used to compare the results of the 2 groups. The trend was analyzed using the Mantel-Haenszel statistics. Logistic regression models obtained the estimated age-related probability of fecal incontinence components.

Results: The risk of sphincter injury at first delivery was 3.9%, and the risk of a repeat sphincter injury was 10.0% (odds ratio, 2.70; 95% confidence interval, 1.80-4.07). The overall prevalence of fecal incontinence in women without sphincter injuries was 11.7%, which doubled to 23.8% (odds ratio, 2.27; 95% confidence interval, 1.75-2.94) in those with 1 sphincter injury and more than tripled to 36.1% (odds ratio, 3.97; 95% confidence interval, 3.11-5.07) after 2 sphincter injuries (trend P<.0001). The proportion of women with severe fecal incontinence increased 3-fold and 5-fold from 1.8% after no obstetrical anal sphincter injury to 5.4% (95% confidence interval, 3.3-8.2) and 9.0% (95% confidence interval, 6.1-12.6) after 1 or 2 obstetrical anal sphincter injuries, respectively (trend P<.0001). In women without sphincter injuries, the estimated probability of fecal incontinence increased from 7.0% at the age of 40 years to 19.8% at the age of 60 years. In contrast, in women with 1 or 2 sphincter injuries, the estimated probability of fecal incontinence increased from 26.1% and 33.3%, respectively, at the age of 40 years to 36.8% and 48.8% at the age of 60 years. The prevalence of fecal incontinence increased after 52 years of age in women with 1 or 2 sphincter injuries. The dominant types of leakage in women with fecal incontinence were the combination of liquid stool and gas, and the triple combination consisting of solid and liquid stools and gas. The triple combination increased from 18.9% in those without sphincter injury to 28.2% in women with 2 injuries (trend P=.0204).

Conclusion: The risk of sustaining a repeat sphincter injury at the second delivery was almost tripled compared with the risk at the first delivery. Furthermore, 1 or 2 sphincter injuries brought severe long-term consequences for bowel continence. Accidental leakage of stool and gas increased with each sphincter injury, and the effect was proportionally cumulative. After the age of 52 years, the prevalence of fecal incontinence seemed to accelerate.