| Risk factor | % of total* | No. of deliveries | Adjusted OR (95% CI) | |
|---|---|---|---|---|
| No infection | Infection | |||
| Institution-related | ||||
| No. of cesarean deliveries per hospital per year | ||||
| < 130 | 25.1 | 8165 | 158 | Reference |
| 130-949 | 21.7 | 6910 | 282 | 2.20 (1.79-2.71) |
| 950-1249 | 27.7 | 8861 | 317 | 1.85 (1.50-2.29) |
| ≥ 1250 | 25.5 | 8305 | 154 | 1.39 (1.09-1.79) |
| Area-level | ||||
| Quintile of neighbourhood-level income | ||||
| 1 (lowest) | 20.1 | 6410 | 262 | 1.40 (1.19-1.65) |
| 2 | 18.1 | 5824 | 172 | 1.09 (0.91-1.30) |
| 3-5 | 61.8 | 20 007 | 477 | Reference |
| Maternal demographic characteristics | ||||
| Age, yr | ||||
| < 25 | 18.6 | 5929 | 225 | 1.13 (0.94-1.36) |
| 25-34 | 61.5 | 19 880 | 511 | Reference |
| ≥ 35 | 19.9 | 6432 | 175 | 1.21 (1.01-1.45) |
| Prepregnancy weight, kg | ||||
| < 53.0 | 8.0 | 2603 | 61 | 1.05 (0.78-1.41) |
| 53.0-66.9 | 29.3 | 9519 | 194 | Reference |
| 67.0-76.9 | 16.8 | 5429 | 135 | 1.28 (1.02-1.61) |
| 77.0-86.9 | 12.1 | 3888 | 108 | 1.43 (1.12-1.82) |
| 87.0- 97.9 | 7.8 | 2488 | 85 | 1.86 (1.42-2.43) |
| ≥ 98.0 | 9.5 | 2961 | 186 | 3.63 (2.90-4.54) |
| Missing | 16.6 | 5353 | 142 | 1.52 (1.12-2.06) |
| Marital status | ||||
| Married/common-law | 72.7 | 23 511 | 578 | Reference |
| Single/divorced/separated/widowed | 22.3 | 7116 | 285 | 1.34 (1.13-1.58) |
| Missing | 5.0 | 1614 | 48 | 1.14 (0.83-1.58) |
| Alcohol or drug abuse | ||||
| No | 98.6 | 31 809 | 885 | Reference |
| Yes | 1.4 | 432 | 26 | 1.71 (1.12-2.61) |
| Maternal medical conditions | ||||
| Nonobstetric preexisting health conditions affecting pregnancy | ||||
| No | 80.9 | 26 160 | 676 | Reference |
| Yes | 19.1 | 6081 | 235 | 1.28 (1.09-1.51) |
| Diabetes | ||||
| No | 93.5 | 30 181 | 809 | Reference |
| Preexisting | 0.6 | 196 | 11 | 1.62 (0.86-3.04) |
| Gestational | 5.9 | 1864 | 91 | 1.49 (1.17-1.88) |
| Depression during pregnancy | ||||
| No | 95.6 | 30 826 | 855 | Reference |
| Yes | 4.4 | 1415 | 56 | 1.40 (1.05-1.87) |
| Anticoagulation therapy during pregnancy | ||||
| No | 99.1 | 31 965 | 888 | Reference |
| Yes | 0.9 | 276 | 23 | 2.58 (1.64-4.05) |
| Pregnancy history | ||||
| Parity | ||||
| Primiparous | 49.4 | 15 837 | 539 | Reference |
| Multiparous | 50.6 | 16 404 | 372 | 0.81 (0.69-0.95) |
| Pregnancy characteristics | ||||
| Weight gain during pregnancy, kg | ||||
| < 10.0 | 16.7 | 5372 | 155 | 0.81 (0.66-0.99) |
| 10.0-19.9 | 41.8 | 13 522 | 350 | Reference |
| 20.0-29.9 | 13.6 | 4352 | 142 | 1.26 (1.03-1.54) |
| ≥ 30.0 | 1.9 | 601 | 37 | 2.14 (1.49-3.06) |
| Missing | 26.0 | 8394 | 227 | 1.10 (0.86-1.41) |
| Chorioamnionitis | ||||
| No | 97.8 | 31 569 | 856 | Reference |
| Yes | 2.2 | 672 | 55 | 2.78 (2.07-3.75) |
| Labour | ||||
| Stage of labour before cesarean delivery | ||||
| None | 48.6 | 15 793 | 332 | Reference |
| First | 31.9 | 10 235 | 350 | 1.20 (1.01-1.43) |
| Second | 19.4 | 6213 | 229 | 1.54 (1.27-1.88) |
| Delivery | ||||
| Year of delivery | ||||
| 1997-2000 | 22.0 | 6947 | 342 | 2.31 (1.88-2.84) |
| 2001-2004 | 26.5 | 8607 | 191 | 1.14 (0.91-1.41) |
| 2005-2008 | 27.0 | 8742 | 193 | 1.02 (0.83-1.25) |
| 2009-2012 | 24.5 | 7945 | 185 | Reference |
| Antibiotic therapy during labour and delivery | ||||
| Yes | 62.9 | 20 355 | 506 | Reference |
| No | 37.1 | 11 886 | 405 | 1.30 (1.12-1.51) |
| Maternal blood transfusion | ||||
| No | 99.0 | 31 932 | 885 | Reference |
| Yes | 1.0 | 309 | 26 | 2.70 (1.77-4.12) |
| Fetal and neonatal | ||||
| Gestational age | ||||
| < 37 wk | 9.8 | 3125 | 120 | 1.36 (1.10-1.69) |
| 37 wk to 39 wk + 6 d | 57.1 | 18 475 | 443 | Reference |
| ≥ 40 wk | 33.1 | 10 641 | 348 | 1.09 (0.93-1.28) |
Note: CI = confidence interval, OR = odds ratio.
*A total of 33 152 cesarean deliveries were included in the analysis; 839 deliveries were excluded because of missing values for neighbourhood-level income (n = 724), stage of labour (n = 1) and/or gestational age (n = 118).