Table 1. First pregnancy characteristics for women according to their exposure status.
| First pregnancy characteristic | Initial 3rd or 4th degree tear n (%) (N = 5174) |
No 3rd or 4th degree tear n (%) (N = 177271) |
Unadjusted OR (99%CI) | Adjusted ORa (99%CI) |
|---|---|---|---|---|
| Second pregnancy | ||||
| Yes | 3333 (64.4) | 118681 (66.9) | 0.89 (0.83–0.96) | 0.98 (0.89–1.09) |
| No | 1841 (35.6) | 58590 (33.1) | ||
| Age at delivery | ||||
| Missing = 2 | ||||
| Mean (SD) | 27.6 (5.6) | 25.9 (6.0) | 1.05 (1.04–1.06) | 1.04 (1.03–1.05) |
| Body mass index | ||||
| Missing = 106231 | ||||
| Mean (SD) | 25.0 (4.8) | 25.0 (5.0) | 1.00 (0.99–1.01) | 1.00 (0.99–1.01) |
| Deprivation | ||||
| Missing = 529 | ||||
| Most deprived | 2765 (53.6) | 102433 (58.0) | 0.84 (0.78–0.90) | 0.97 (0.88–1.07) |
| Least deprived | 2395 (46.4) | 74323 (42.0) | 1 | 1 |
| Smoking status | ||||
| Missing = 12763 | ||||
| Non smoker | 3506 (73.5) | 105038 (63.7) | 1 | 1 |
| Smoker | 671 (14.1) | 40695 (24.7) | 1.79 (1.47–2.18) | 0.65 (0.56–0.75) |
| Ex-smoker | 590 (12.4) | 19182 (11.6) | 1.54 (1.20–1.97) | 0.96 (0.84–1.11) |
aMultivariate analyses adjusted for age at delivery, BMI, deprivation, smoking (all in the first pregnancy)
Missing data not included in the proportions presented