Prevalence and Predictors of Anal Incontinence 9-12 Months Postpartum in Primipara with Vacuum-Assisted Deliveries

We have examined prospectively a large cohort of primipara with VA deliveries and previously reported that approximately one in five had an anal sphincter injury of which one quarter were clinically unrecognized. In this paper, we examine the development and potential predictors of postpartum anal incontinence (AI) in the cohort. We hypothesized that both clinically recognized and unrecognized anal sphincter injuries would be associated with AI development.

The participants were interviewed 9-12 months postpartum using the St. Marks incontinence score (SMIS). The primary outcome was the prevalence of de novo AI development defined as SMIS > 0. Logistic regression analysis was used to calculate the odds ratios for selected variables.

Of 334 eligible women, 271 (81%) were initially included in the study and 248 of them (92%) completed the interview. The prevalence of de novo AI was 21.8% (95% CI 16.4-28.4). Both clinically recognized and unrecognized anal sphincter injuries increased the odds significantly about threefold. Only 35.2% of the symptomatic women had a sphincter injury, and we identified no predictors in the rest.

Approximately one in five primipara undergoing a VA delivery developed AI. About one third of them were associated with either a clinically recognized or unrecognized anal sphincter injury. Thus, the combination of the two provides the most clinically relevant distinction between anal sphincter injury dependent and independent predictors of AI development. In the symptomatic women with no sphincter injuries, we found no predictive variables.