The role of mediolateral episiotomy during labour: analysis of risk factors for obstetric anal sphincter tears.
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.
Aukee
Pauliina
P
Pelvic Floor Research & Therapy Unit, Department of Obstetrics and Gynaecology, Jyväskylä Central Hospital. Jyväskylä. Finland. pauliina.aukee@ksshp.fi
Sundström
Helena
H
Kairaluoma
Matti V
MV
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