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Table 2 Association between mediolateral episiotomy and OASIs according to the type of operative vaginal delivery

From: Mediolateral episiotomy and risk of obstetric anal sphincter injuries and adverse neonatal outcomes during operative vaginal delivery in nulliparous women: a propensity-score analysis

  Total number of women Mediolateral episiotomy No Mediolateral episiotomy RR (95% CI)
  Number of women Number (%) with OASIs Number of women Number (%) with OASIs Univariate analysis * Using IPTW *
Whole population 7589 2880 52 (1.8) 4709 203 (4.3) 0.40 (0.29–0.56) 0.33 (0.27–0.41)
Forceps/spatula delivery 2698 1433 33 (2.3) 1265 86 (6.8) 0.34 (0.22–0.54) 0.38 (0.28–0.52)
Vacuum delivery 4853 1421 18 (1.3) 3432 117 (3.4) 0.31 (0.18–0.52) 0.27 (0.20–0.38)
  1. RR risk ratio, CIs confidence intervals, IPTW inverse probability of treatment weighting, OASIs obstetric anal sphincter injuries. * Mixed model. Missing data – mode of operative vaginal deliveries: n = 38. Covariates used to estimate the propensity score: induction of labour, epidural analgesia, occiput posterior position, prolonged pregnancy defined as > 41 weeks of gestation, fetal distress, type of instruments (forceps/spatula delivery and vacuum delivery), birth weight as a proxy of prenatal suspicion of large for gestational age, year of delivery and level of maternity unit