Table 2.
Model A: Stratified analyses of eight strata of combinations of oxytocin augmentation, episiotomy, instrumental delivery and birth weights <4000 g, and four strata of episiotomy, instrumental delivery and birth weights ≥4000 g, independent of oxytocin augmentation
| Group | Oxytocin augmentation* | Episiotomy* | Operative vaginal delivery* | Birth weight† | Women N |
OASI‡ N (%) |
OR | 95% CI |
|---|---|---|---|---|---|---|---|---|
| 1 | − | − | − | − | 5328 | 198 (3.7) | 1.0 | |
| 2 | − | + | − | − | 1434 | 60 (4.2) | 1.1 | 0.8 to 1.5 |
| 3 | − | + | + | − | 537 | 43 (8.0) | 2.3 | 1.6 to 3.2 |
| 4 | − | − | + | − | 316 | 47 (14.9) | 4.5 | 3.2 to 6.4 |
| 5 | + | + | + | − | 1283 | 92 (7.2) | 2.0 | 1.6 to 2.6 |
| 6 | + | − | + | − | 896 | 103 (11.5) | 3.4 | 2.6 to 4.3 |
| 7 | + | − | − | − | 2621 | 148 (5.6) | 1.6 | 1.3 to 1.9 |
| 8 | + | + | − | − | 1039 | 61 (5.9) | 1.6 | 1.2 to 2.2 |
| 9 | +/– | + | − | + | 418 | 40 (9.6) | 2.7 | 1.9 to 3.9 |
| 10 | +/− | − | − | + | 977 | 104 (10.6) | 3.1 | 2.4 to 4.0 |
| 11 | +/− | + | + | + | 393 | 55 (14.0) | 4.2 | 3.1 to 5.8 |
| 12 | +/− | − | + | + | 234 | 62 (26.5) | 9.3 | 6.8 to 12.9 |
Crude OR and 95% CIs.
*Used (+)/unused (−).
†≥4000 g (+)/<4000 g (−).
‡Obstetric anal sphincter injury.