| Univariable Analysis | Multivariable Analysis | |||
| All Cesarean Deliveries | OR (95% Cl) | P Value | OR (95% Cl) | P Value |
| Age | ||||
| ≤18 years old | 1.79 (1.60 - 2.00) | <0.0001 | 1.62 (1.45 - 1.82) | <0.0001 |
| 19 - 34 years old | Reference | Reference | ||
| ≥35 years old | 0.92 (0.88 - 0.96) | 0.0003 | 0.91 (0.87 - 0.95) | <0.0001 |
| ASA PS class | ||||
| ASA I - II | Reference | Reference | ||
| ASA I - V | 2.48 (2.38 - 2.58) | <0.0001 | 2.34 (2.24 - 2.43) | <0.0001 |
| Time of day | ||||
| Day shift (07:00 - 17:00) | Reference | Reference | ||
| After hours (17:01 - 06:59) | 1.69 (1.63 - 1.75) | <0.0001 | 1.42 (1.37 - 1.48) | <0.0001 |
| Day of week | ||||
| Weekday | Reference | Reference | ||
| Weekend | 1.43 (1.36 - 1.50) | <0.0001 | 1.24 (1.19 - 1.31) | <0.0001 |
| Urban versus rural | ||||
| Urban | Reference | - | ||
| Rura | 1.08 (1.03 - 1.12) | 0.0003 | ||
| Unknown | 1.36 (1.27 - 1.45) | <0.0001 | ||
| Facility type | ||||
| University hospital | Reference | Reference | ||
| Large community | 0.52 (0.49 - 0.56) | <0.0001 | 0.49 (0.46 - 0.53) | <0.0001 |
| Medium-sized community | 0.73 (0.69 - 0.77) | <0.0001 | 0.76 (0.72 - 0.81) | <0.0001 |
| Other facility | 0.61 (0.58 - 0.65) | <0.0001 | 0.67 (0.63 - 0.72) | <0.0001 |
| Unknown facility | 0.39 (0.35 - 0.43) | <0.0001 | 0 (0 to ∞) | 0.85 |
| US region | ||||
| Northeast | Reference | Reference | ||
| Midwest | 1.10 (1.04 - 1.16) | 0.0014 | 1.25 (1.17 - 1.33) | <0.0001 |
| South | 1.20 (1.15 - 1.26) | <0.0001 | 1.34 (1.27 - 1.41 | <0.0001 |
| West | 0.75 (0.70 - 0.81) | <0.0001 | 0.77 (0.71 - 0.83) | <0.0001 |
| Unknown region | 0.61 (0.55 - 0.67) | <0.0001 | 0 (0 to ∞) | 0.84 |
| CD volume per year | ||||
| Volume ≤ 1000 | Reference | - | ||
| Volume > 1000 | 0.94 (0.91 - 0.98) | 0.0054 | - | - |
| Emergency status | ||||
| Not emergency | Reference | Reference | ||
| Emergency | 3.18 (3.03 - 3.34) | <0.0001 | 2.96 (2.81 - 3.12) | <0.0001 |
| TOLAC | ||||
| Not TOLAC | Reference | Reference | ||
| TOLAC | 0.32 (0.22 - 0.47) | <0.0001 | 0.31 (0.21 - 0.46) | <0.0001 |
| Year of CD | ||||
| 2010 | Reference | Reference | ||
| 2011 | 0.95 (0.88 - 1.02) | 0.1360 | 0.92 (0.86 - 0.99 | 0.02 |
| 2012 | 1.04 (0.97 - 1.10) | 0.2700 | 1.00 (0.94 - 1.06) | 0.96 |
| 2013 | 1.04 (0.97 - 1.10) | 0.2900 | 0.99 (0.93 - 1.06 | 0.82 |
| 2014 | 0.90 (0.84 - 0.95) | 0.0005 | 0.88 (0.82 - 0.94) | <0.0001 |
| 2015 | 0.75 (0.66 - 0.85) | <0.0001 | 0.74 (0.65 - 0.84) | <0.0001 |