title: The role of mediolateral episiotomy during labour: analysis of risk factors for obstetric anal sphincter tears.
abstract: BACKGROUND
  To determine risk factors for third-degree and complete third- or fourth-degree anal sphincter tears in vaginal delivery.
  
  
  METHODS
  This is a retrospective comparative study. Fifty-three women who had sustained an anal sphincter tear were compared with 9,178 women without such a complication between August 1997 and October 2001. Obstetric data was collected from an electronic database. The main outcome measures were odds ratios.
  
  
  RESULTS
  In the whole study population, odds ratios (ORs) for third-degree tears were: primiparity, 8.34 (95% confidence interval [CI] 3.98-17.48); vacuum extraction, 5.22 (95% CI 2.69-10.13); parietal presentation, 3.97 (95% CI 1.16-13.64); and birth weight >4,000 g, 3.77 (95% CI 2.11-6.68); and for complete third- or fourth-degree tears odds ratios were 5.42, 2.98, 5.64, and 3.01, respectively. In multivariate analysis, mediolateral episiotomy appeared to be protective as regards third-degree tears (OR 0.37 [95% CI 0.2020-0.70]).
  
  
  CONCLUSIONS
  Vacuum-assisted vaginal delivery bears an increased risk of third-degree anal sphincter tears in a maternity unit where forceps are not used. Restricted use of mediolateral episiotomy may have a protective effect on the perineum.
authors.affiliation: Pelvic Floor Research & Therapy Unit, Department of Obstetrics and Gynaecology, Jyväskylä Central Hospital. Jyväskylä. Finland. pauliina.aukee@ksshp.fi
authors.forename: Pauliina
authors.initials: P
authors.lastname: Aukee
authors.forename: Helena
authors.initials: H
authors.lastname: Sundström
authors.forename: Matti V
authors.initials: MV
authors.lastname: Kairaluoma
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000293:injuries*; D016022:Case-Control Studies; D004841:Episiotomy; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D015601:Injury Severity Score; D022125:Lacerations / Q000453:epidemiology / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D007744:Obstetric Labor Complications / Q000453:epidemiology / Q000209:etiology* / Q000473:pathology / Q000517:prevention & control*; D016017:Odds Ratio; D011247:Pregnancy; D011256:Pregnancy Outcome; D012189:Retrospective Studies; D012307:Risk Factors; D014620:Vacuum Extraction, Obstetrical / Q000009:adverse effects