The purpose of this study was to estimate the incidence of urinary and bowel incontinence in relation to anal sphincter laceration in primiparous women and to identify factors that are associated with anal sphincter laceration in a unit that uses primarily midline episiotomy. From January 1, 1997, to March 30, 2000, 2941 questionnaires concerning pelvic floor function 6 months after delivery were mailed to primiparous women who were delivered vaginally at the University of Michigan Medical Center. Charts were reviewed for 2858 deliveries to assess the use of episiotomy and the degree of perineal trauma, along with demographic and pertinent delivery variables. There were 943 women who completed the urinary function questionnaire and 831 women who completed the bowel function questionnaire. Univariate analysis was performed on all covariates. Multiple logistic regression was used for the analysis of the presence of third- or fourth-degree lacerations as the outcome. Nineteen percent of the women who completed the survey had sustained third- or fourth-degree lacerations during childbirth. The women in the sphincter laceration group were more likely (23.0%) to have bowel incontinence than the women in the control group (13.4%) ( P<.05). The incidence of worse bowel control was nearly 10 times higher in women with fourth-degree lacerations (30.8%) compared with women with third-degree lacerations (3.6%, P<.001). Macrosomia (odds ratio, 2.19; 95% CI, 1.61, 2.99), forceps-assisted delivery (odds ratio, 4.75; 95% CI, 3.43, 6.57), and vacuum-assisted delivery (odds ratio, 3.51; 95% CI, 2.64, 4.66) were associated with higher risks of third- and fourth-degree lacerations. Midline episiotomy (odds ratio, 2.24; 95% CI, 1.81, 2.77), but not mediolateral (odds ratio, 0.66; 95% CI, 0.375, 1.19), episiotomy was associated with anal sphincter lacerations. More than one half of the women had new onset of urinary incontinence after delivery and reported several lifestyle modifications to prevent leakage. Women with third- and fourth-degree lacerations were more likely to have bowel incontinence than women without anal sphincter lacerations. Fourth-degree lacerations appear to affect anal continence greater than third-degree lacerations.