Cox regression results for risk factors for undergoing surgical treatment for UI
| Risk factor | No operation (N=32 501) | UI operation (N=762) | Unadjusted | Adjusted | ||
| N (%) | N (%) | HR (95% CI) | p Value | HR (95% CI) | p Value | |
| Mode of delivery | ||||||
| SVD/breech only | 19 776 (60.8%) | 533 (69.9%) | 1.00 | 1.00 | ||
| CS only | 2524 (7.8%) | 18 (2.4%) | 0.40 (0.25 to 0.64) | <0.001 | 0.51 (0.32 to 0.83) | 0.007 |
| Instrumental (at least one forceps) | 8433 (25.9%) | 172 (22.6%) | 0.86 (0.72 to 1.02) | 0.08 | 0.86 (0.72 to 1.03) | 0.10 |
| Instrumental (at least one, but no forceps) | 639 (2.0%) | 12 (1.6%) | 1.72 (0.97 to 3.05) | 0.06 | 1.65 (0.93 to 2.94) | 0.09 |
| SVD+CS | 1129 (3.5%) | 27 (3.5%) | 1.12 (0.76 to 1.65) | 0.57 | 1.07 (0.73 to 1.58) | 0.72 |
| Age at first delivery | ||||||
| Under 20 years | 5510 (17.0%) | 182 (23.9%) | 1.28 (1.08 to 1.52) | 0.004 | 1.25 (1.05 to 1.48) | 0.011 |
| 20–29 years | 22 221 (68.4%) | 519 (68.1%) | 1.00 | 1.00 | ||
| 30–49 years | 4770 (14.7%) | 61 (8.0%) | 0.82 (0.63 to 1.07) | 0.14 | 1.00 (0.76 to 1.31) | 0.98 |
| Total number of deliveries | ||||||
| Single | 8306 (25.6%) | 126 (16.5%) | 1.00 | 1.00 | ||
| 2–4 | 23 323 (71.8%) | 614 (80.6%) | 1.63 (1.35 to 1.97) | <0.001 | 1.45 (1.18 to 1.77) | <0.001 |
| 5+ | 872 (2.7%) | 22 (2.9%) | 1.17 (0.74 to 1.84) | 0.51 | 0.98 (0.62 to 1.56) | 0.93 |
| Twins at some point | ||||||
| No | 32 044 (98.6%) | 754 (99.0%) | 1.00 | |||
| Yes | 457 (1.4%) | 8 (1.0%) | 0.70 (0.35 to 1.41) | 0.32 | ||
| Time between deliveries | ||||||
| One delivery | 8306 (25.6%) | 126 (16.5%) | 1.00 | |||
| All <2 years | 3883 (11.9%) | 97 (12.7%) | 1.57 (1.20 to 2.04) | 0.001 | ||
| All ≥2 years | 15 463 (47.6%) | 393 (51.6%) | 1.63 (1.33 to 1.99) | <0.001 | ||
| Mixture | 4849 (14.9%) | 146 (19.2%) | 1.59 (1.25 to 2.01) | <0.001 | ||
| Type of perineal wound | ||||||
| No wound | 13 601 (41.8%) | 265 (34.8%) | 1.00 | 1.00 | ||
| All episiotomy | 8852 (27.2%) | 239 (31.4%) | 1.32 (1.11 to 1.58) | 0.002 | 1.22 (1.01 to 1.46) | 0.035 |
| At least one third-degree tear | 150 (0.5%) | 2 (0.3%) | 0.90 (0.22 to 3.62) | 0.88 | 0.81 (0.20 to 3.24) | 0.76 |
| No perineal tears (lacerations only) | 9898 (30.5%) | 256 (33.6%) | 1.53 (1.29 to 1.82) | <0.001 | 1.31 (1.10 to 1.57) | 0.003 |
CS, caesarean section; SVD, spontaneous vaginal delivery; UI, urinary incontinence.