title: Obstetric events leading to anal sphincter damage.
abstract: OBJECTIVE
  To identify the obstetric factors relating to anal sphincter injury at first vaginal delivery by prospective cohort study of primiparous women.
  
  
  METHODS
  We compared the results of a bowel function questionnaire and anal vector manometry before and 6 weeks after delivery in 184 primiparous women. Postpartum, pudendal nerve conduction latency was measured in all women, and anal endosonography was performed in 81 with altered fecal continence or abnormal physiology.
  
  
  RESULTS
  Sixteen (9%) women, none of whom had altered fecal continence, were delivered by cesarean. After vaginal delivery, 42 of 168 (25%) women had impairment of fecal continence and 76 of 168 (45%) women had abnormal anal physiology. Instrumental vaginal delivery was associated with an 8.1-fold (95% confidence interval [CI] 2.7, 24.0; P < .001) risk of anal sphincter injury and a 7.2-fold (95% CI 2.8, 18.6; P < .001) risk of symptoms. Duration of the second stage of labor beyond 60 minutes led to a 1.7-fold (95% CI 1.14, 2.48; P;< .01) risk of anal sphincter injury and a 1.6-fold (95% CI 1.03, 2.6, P = .01) risk of symptoms. Epidural analgesia, used in 58% of vaginal deliveries, prolonged the second stage of labor (P = .004; odds ratio [OR] 7.7; 95% CI 4.0, 14.7) and was associated with increased risk of sphincter injury (P = .02; OR 2.1; 95% CI 1.1, 4.0) and of symptoms (P = .02; OR 2.0; 95% CI 1.1, 3.7).
  
  
  CONCLUSIONS
  Instrumental delivery and a second stage of labor prolonged by epidural analgesia are the obstetric factors that pose the greatest risk of injury to the anal sphincter mechanism in primiparous vaginal delivery.
authors.affiliation: Department of Obstetrics and Gynaecology, University College Dublin, National Maternity Hospital, Ireland.
authors.forename: V
authors.initials: V
authors.lastname: Donnelly
authors.forename: M
authors.initials: M
authors.lastname: Fynes
authors.forename: D
authors.initials: D
authors.lastname: Campbell
authors.forename: H
authors.initials: H
authors.lastname: Johnson
authors.forename: P R
authors.initials: PR
authors.lastname: O'Connell
authors.forename: C
authors.initials: C
authors.lastname: O'Herlihy
mesh_terms: D001003:Anal Canal / Q000000981:diagnostic imaging / Q000293:injuries* / Q000503:physiopathology; D036861:Delivery, Obstetric / Q000009:adverse effects*; D005242:Fecal Incontinence / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D016015:Logistic Models; D008365:Manometry; D009130:Muscle, Smooth / Q000293:injuries / Q000503:physiopathology; D011247:Pregnancy; D011446:Prospective Studies; D011795:Surveys and Questionnaires; D014463:Ultrasonography