Table 6 Maternal risk factors by census dissemination area income quintile
| Â | Census dissemination area average income quintile | Â | Â | Â | Â | Â |
|---|---|---|---|---|---|---|
| Â | 1 (lowest) | 2 | 3 | 4 | 5 (highest) | 2-sided p |
n | 11444 | 11510 | 11953 | 12163 | 11969 | Â |
| Â | Â | Â | n (%) | Â | Â | Â |
Smoking during pregnancy | 690 (6) | 807 (7) | 815 (7) | 698 (6) | 468 (4) | <0.0001 |
Maternal age | Â | Â | Â | Â | Â | Â |
 <20 | 269 (2) | 211 (2) | 201 (2) | 144 (1) | 102 (1) | <0.0001 |
 20–35 | 8714 (76) | 8667 (75) | 8827 (74) | 8738 (72) | 7729 (65) |  |
 ≥ 35 | 2461 (22) | 2632 (23) | 2925 (24) | 3281 (27) | 4138 (35) |  |
Parity ≥ 1 | 5713 (50) | 5643 (49) | 5979 (50) | 6119 (50) | 6089 (51) | .0760 |
Pre-pregnancy BMI | Â | Â | Â | Â | Â | Â |
 Underweight (<18.5) | 1092 (10) | 878 (8) | 772 (6) | 691 (6) | 665 (6) | <0.0001 |
 Normal weight (18.5–25) | 7190 (63) | 7167 (62) | 7355 (62) | 7727 (64) | 8279 (69) |  |
 Overweight (25–30) | 2144 (19) | 2278 (20) | 2464 (21) | 2471 (20) | 2137 (18) |  |
 Obese (≥30) | 1018 (9) | 1187 (10) | 1362 (11) | 1274 (10) | 888 (7) |  |
Height (cm) – Mean (SD) | 162 (7) | 163 (7) | 164 (7) | 165 (7) | 165 (7) | <0.0001 |
Diabetes/ Hypertension | Â | Â | Â | Â | Â | Â |
 Neither | 9388 (82) | 9592 (83) | 10061 (84) | 10493 (86) | 10629 (89) | <0.0001 |
 Diabetes only | 1444 (13) | 1270 (11) | 1188 (10) | 984 (8) | 729 (6) |  |
 Hypertension only | 463 (4) | 512 (4) | 563 (5) | 577 (5) | 538 (4) |  |
 Diabetes & hypertension | 149 (1) | 136 (1) | 141 (1) | 109 (1) | 73 (1) |  |
Oligohydramnios | 308 (3) | 281 (2) | 264 (2) | 258 (2) | 272 (2) | 0.0345 |
Placenta disorder | 238 (2) | 274 (2) | 239 (2) | 245 (2) | 255 (2) | 0.2528 |