title: Defining an at-risk population for obstetric anal sphincter laceration.
abstract: OBJECTIVE
  The purpose of this study was to calculate the number of cesarean deliveries needed to prevent 1 case of obstetric anal sphincter laceration associated with operative vaginal delivery in an at-risk cohort.
  
  
  METHODS
  An institutional, computerized database was used to analyze women with obstructed labor who could have been managed by either operative vaginal or cesarean delivery from September 2006 to March 2008. Women with 1 or more of the following diagnoses comprised the cohort: cephalopelvic disproportion (CPD), arrest of descent, maternal exhaustion, and fetal distress.
  
  
  RESULTS
  Fifty (23.9%) out of a total of 209 women managed by operative vaginal delivery experienced an anal sphincter laceration compared to none of 254 women in the cesarean delivery group (P < .0001). The ARR therefore was 23.9% (95% confidence interval, 18.1-29.7) and the NNT was 4.2 (95% confidence interval, 3.4-5.5).
  
  
  CONCLUSIONS
  Five cesarean deliveries are needed to prevent 1 anal sphincter laceration associated with operative vaginal delivery in this cohort.
authors.affiliation: Department of Obstetrics and Gynecology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, USA.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Minaglia
authors.forename: Chieko
authors.initials: C
authors.lastname: Kimata
authors.forename: Karen A
authors.initials: KA
authors.lastname: Soules
authors.forename: Tamara
authors.initials: T
authors.lastname: Pappas
authors.forename: Ian A
authors.initials: IA
authors.lastname: Oyama
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000293:injuries*; D002585:Cesarean Section / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D022125:Lacerations / Q000453:epidemiology* / Q000517:prevention & control*; D007744:Obstetric Labor Complications / Q000601:surgery*; D011247:Pregnancy; D018570:Risk Assessment