| |
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)
|
- 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
