Objective
To evaluate whether antepartum pelvic floor muscle strength, as measured by the Brink scale, predicts postpartum anal incontinence.
Study Design
This prospective cohort study of primigravid women used validated questionnaires and standardized pelvic examinations to evaluate subjects during the third trimester and at 2 postpartum time points.
Results
Of the initial 129 subjects, 102 and 81 completed 2 week and 6 month postpartum visits. 35% had cesarean deliveries. The antepartum prevalence of fecal incontinence (14%) did not differ significantly from the postpartum (17% at 2 weeks, 11% at 6 months). However, the prevalence of flatal incontinence fell from antepartum (65%) to postpartum (47% at 2 weeks, P = .001; 49% at 6 months, P = .012). Mean Brink score decreased postpartum; no correlations were found between Brink score and questionnaire scores.
Conclusion
Anal incontinence symptoms are common in the third trimester of a first pregnancy and may regress or resolve after delivery. Brink score did not predict postpartum anal incontinence.
Anal incontinence, defined as the involuntary loss of stool or flatus, is an embarrassing and socially isolating condition. Estimates of prevalence in community-dwelling adults vary widely, and depend greatly on symptom definition. Some studies suggest that women are at higher risk for anal incontinence than men, and speculation has been that the difference is due to obstetric trauma.
In addition to the general risk factors of advancing age, chronic illness, loose stools, and urinary incontinence, an important risk factor for anal incontinence in young women is anal sphincter laceration, which may occur in up to 18% of vaginal deliveries. Rates of anal incontinence after repair of recognized anal sphincter lacerations are reported to range from 15-59%. Numerous factors have been associated with anal sphincter laceration during childbirth, including nulliparity, increased birthweight, midline episiotomy, and operative vaginal deliveries.
There is also growing recognition that pregnancy itself may contribute to the development of pelvic floor disorders. Many patients and obstetricians argue that an elective cesarean delivery will prevent anal incontinence, but women can have altered fecal continence despite cesarean delivery or after vaginal delivery without sphincter laceration. The anal sphincter is only 1 component of a complex anal continence mechanism, which also involves pelvic floor muscle function, stool consistency/volume, and colonic transit. The aim of this study was to determine whether pelvic floor muscle strength in the third trimester, as measured by the Brink scale, would predict postpartum anal incontinence.
Materials and Methods
After obtaining approval from the Oregon Health and Science University Institutional Review board, we performed a prospective cohort study in primigravid women. Eligible subjects were recruited in the third trimester of their first pregnancy. We excluded potential subjects if they had any contraindication to a spontaneous vaginal delivery, known genitourinary abnormalities, prior vaginal surgery, or multiple gestation. After obtaining informed consent, subjects were evaluated during the third trimester and at 2 weeks postpartum by physical examination and validated, symptom-specific questionnaires. They then repeated the questionnaires by mail at 6 months postpartum. Labor and delivery data were collected.
Anal incontinence was assessed with the Fecal Incontinence Severity Index (FISI), which measures the frequency of 4 symptoms (incontinence of gas, mucus, liquid stool, and solid stool) using the following scale: 2 or more times a day, once a day, 2 or more times a week, once a week, 1-3 times per month, or never. For this study, we used the patient-based weighting of severity; a maximum score is 61.
As accepted by the Pelvic Floor Disorders Network, fecal incontinence was defined as involuntary leakage of liquid or solid stool greater than or equal to 1 episode per month as reported on the FISI. Flatal incontinence (≥1 episode per month) was reported as a separate entity. The term “anal incontinence” connotes fecal incontinence, flatal incontinence, or both. Urinary incontinence was also assessed with validated questionnaires.
Examiners blinded to questionnaire scores, but not to pregnancy status, performed standardized examinations in the dorsal lithotomy position at the antepartum and 2-week postpartum visits. Pelvic floor muscle strength was measured using the Brink scale and a perineometer. After inserting 2 lubricated fingers into the vagina, the examiner asked subjects to “squeeze and hold their pelvic muscles.” The Brink scale assesses 3 separate pelvic floor muscle contraction variables: vaginal pressure, displacement of the examiner’s fingers (ie, range of motion), and duration of contraction. Each subscale is a 4-point ordinal scale with a minimum score of 1 and maximum of 4. The scores are summed to provide a total score that ranges from 3 to 12. After the digital evaluation and recording of the scores, the Peritron perineometer (Cardio Design Pty Ltd, Oakleigh, Victoria, Australia) was used to obtain baseline and maximum squeeze pressures.
The current study was part of a cohort study evaluating risk factors for anal sphincter laceration; however, a separate sample size calculation was used to determine whether antepartum Brink score predicted anal incontinence at 6 months postpartum, based on the following assumptions. Previous epidemiologic studies in Oregon suggest a postpartum anal incontinence prevalence of 15-25% after a vaginal delivery. For the Brink score, we extrapolated from urinary incontinence data suggesting a mean score of 5.5 (standard deviation [SD] 1.5) in women with postpartum urinary incontinence and 7 (SD 1.5) in women without. Using these expected Brink scores, 17 vaginally delivered women with and without anal incontinence at 6 months postpartum would be required to detect a 1.5-point difference in Brink score between the 2 groups (alpha .05; power 0.80). Assuming a postpartum anal incontinence prevalence of 20%, a cesarean delivery rate of 15% in these uncomplicated primigravid women, and an attrition rate of 15%, we aimed to enroll 125 women.
For paired observations, we used the Wilcoxon signed ranks test to compare continuous data and the McNemar test to compare categorical data. The Hodges-Lehmann estimate of shift parameters based on the Mann-Whitney U test was used to compare Brink and perineometer scores between the 2 groups. Spearman correlations were used to compare pelvic floor strength testing and symptoms. A 2-sided P < .05 was considered statistically significant. Analyses were performed with SPSS 11.0 (SPSS Inc, Chicago, IL) and Stata 10.0 (Stata Corp, College Station, TX).
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