Variable | Cases N=1119 | Controls N=209 941 | Unadjusted OR (95% CI) | Adjusted* OR (95% CI) |
---|---|---|---|---|
Parity | ||||
Multiparous | 628 (56.1) | 119 156 (56.8) | 1.0 | 1.0 |
Primiparous | 491 (43.9) | 90 785 (43.2) | 1.03 (0.91 to 1.16) | 1.36 (1.18 to 1.57) |
Multiple pregnancy | ||||
No | 1073 (95.9) | 206 235 (98.2) | 1.0 | 1.0 |
Yes | 46 (4.1) | 3706 (1.8) | 2.39 (1.77 to 3.21) | 2.30 (1.71 to 3.10) |
Coexisting medical condition | ||||
No | 974 (87.0) | 190 722 (90.9) | 1.0 | 1.0 |
Yes | 145 (13.0) | 19 219 (9.2) | 1.48 (1.24 to 1.76) | 1.39 (1.16 to 1.65) |
Ultrasound before 13 weeks gestation | ||||
Yes | 827 (73.9) | 150 535 (71.7) | 1.0 | † |
No | 276 (24.7) | 54 977 (26.2) | 0.91 (0.80 to 1.05) | |
Missing | 16 (1.4) | 4429 (2.1) | 0.66 (0.40 to 1.08) | |
Past caesarean section | ||||
0 | 862 (77.0) | 177 341 (84.5) | 1.0 | 1.0 |
≥1 | 257 (23.0) | 32 600 (15.5) | 1.62 (1.41 to 1.87) | 1.79 (1.53 to 2.10) |
Past ectopic pregnancy | ||||
0 | 1094 (97.8) | 207 007 (98.6) | 1.0 | † |
≥1 | 25 (2.2) | 2934 (1.4) | 1.63 (1.09 to 2.42) | |
Past spontaneous abortion | ||||
0 | 827 (73.9) | 165 832 (79.0) | 1.0 | 1.0 |
1–2 | 259 (23.2) | 40 301 (19.2) | 1.29 (1.12 to 1.48) | 1.25 (1.08 to 1.44) |
≥3 | 33 (3.0) | 3808 (1.8) | 1.74 (1.23 to 2.46) | 1.57 (1.10 to 2.24) |
Mode of delivery | ||||
Spontaneous vaginal/ instrumental vaginal | 563 (50.3) | 145 915 (69.5) | 1.0 | † |
Planned caesarean | 224 (20.0) | 34 742 (16.6) | 1.67 (1.43 to 1.95) | |
Unplanned caesarean | 332 (29.7) | 29 284 (14.0) | 2.94 (2.56 to 3.37) | |
ICU/HDU admission | ||||
No | 850 (76.0) | 208 718 (99.4) | 1.0 | † |
Yes | 269 (24.0) | 1223 (0.6) | 54. 01 (46.57 to 62.64) |
*Variables included in the multivariable model: socioeconomic quintile, maternal age, country of birth, ATSI status, parity, multiple pregnancy, coexisting medical condition, past caesarean section and past spontaneous abortion.
†Not included in multivariable model as either it did not contribute significantly to the fit of the model, or was on the causal pathway (mode of delivery) or considered an outcome (ICU/HDU admission).
ATSI, Aboriginal and Torres Strait Islander; HDU, high dependency unit; ICU, intensive care unit.