Characteristics | Study cohort | Respondents | No survey | p-value* | Univariate odds ratio |
---|---|---|---|---|---|
 | N = 1989 (%) | N = 913 (%) | N = 1076 (%) |  | (95 % CI)a |
Maternal age (years) | Â | Â | Â | Â | Â |
 ≤24 | 233 (11.7) | 66 (7.2) | 167 (15.5) | p < 0.0001 | 0.50 (0.36–0.71) |
 25–29 | 487 (24.5) | 214 (23.4) | 273 (25.4) |  | Reference |
 30–34 | 750 (37.7) | 362 (39.7) | 388 (36.1) |  | 1.19 (0.95–1.50) |
 ≥35 | 519 (26.1) | 271 (29.7) | 248 (23.1) |  | 1.39 (1.09–1.79) |
Country of birth | Â | Â | Â | Â | Â |
 Australia | 1196 (60.1) | 559 (61.2) | 637 (59.2) | p = 0.4 | Reference |
 Other | 793 (39.9) | 354 (38.8) | 439 (40.8) |  | 0.92 (0.77–1.10) |
Socio-economic index | Â | Â | Â | Â | Â |
 1 (lowest) | 107 (5.4) | 30 (3.3) | 77 (7.2) | p < 0.0001 | 0.34 (0.22–0.53) |
 2 | 395 (19.9) | 142 (15.6) | 253 (23.5) |  | 0.49 (0.39–0.63) |
 3 | 169 (8.5) | 66 (7.2) | 103 (9.6) |  | 0.56 (0.40–0.79) |
 4 | 463 (23.3) | 220 (24.1) | 243 (22.6) |  | 0.80 (0.64–1.00) |
 5 (highest) | 855 (43.0) | 455 (49.8) | 400 (37.2) |  | Reference |
Maternity unit | Â | Â | Â | Â | Â |
 1 | 37 (1.9) | 16 (1.8) | 21 (2.0) | p < 0.0001 | 1.37 (0.70–2.67) |
 2 | 674 (33.9) | 241 (26.4) | 433 (40.2) |  | Reference |
 3 | 585 (29.4) | 280 (30.7) | 305 (28.4) |  | 1.65 (1.32–2.07) |
 4 | 29 (1.5) | 17 (1.9) | 12 (1.1) |  | 2.55 (1.20–5.42) |
 5 | 245 (12.3) | 133 (14.6) | 112 (10.4) |  | 2.13 (1.59–2.87) |
 6 | 149 (7.5) | 75 (8.2) | 74 (6.9) |  | 1.82 (1.27–2.60) |
 7 | 270 (13.6) | 151 (16.5) | 119 (11.1) |  | 2.28 (1.71–3.04) |
Parity | Â | Â | Â | Â | Â |
 Nulliparous | 923 (46.4) | 460 (50.4) | 463 (43.0) | p = 0.001 | 1.34 (1.13–1.61) |
 Multiparous | 1066 (53.6) | 453 (49.6) | 613 (57.0) |  | Reference |
Maternal smoking in pregnancy | 140 (7.0) | 25 (2.7) | 115 (10.7) | p < 0.0001 | 0.24 (0.15–0.37) |
Maternal BMI | Â | Â | Â | Â | Â |
 ≤25 | 1283 (64.5) | 609 (66.7) | 674 (62.6) | p = 0.1 | Reference |
 >25, ≤ 30 | 438 (22.0) | 193 (21.1) | 245 (22.7) |  | 0.87 (0.70–1.10) |
 >30 | 268 (13.5) | 111 (12.2) | 157 (14.6) |  | 0.78 (0.60–1.02) |
Multiple pregnancy | 28 (1.4) | 13 (1.4) | 15 (1.4) | p = 1.0 | 1.02 (0.48–2.16) |
Mode of birth | Â | Â | Â | Â | Â |
 Vaginal | 1148 (57.7) | 530 (58.1) | 618 (57.5) | p = 0.1 | Reference |
 Instrumental | 244 (12.3) | 126 (13.8) | 118 (11.0) |  | 1.25 (0.94–1.64) |
 Pre-labour caesarean | 309 (15.5) | 128 (14.0) | 181 (16.8) |  | 0.95 (0.73–1.23) |
 Intrapartum caesarean | 288 (14.5) | 129 (14.1) | 159 (14.8) |  | 0.83 (0.64–1.06) |
Postnatal length of stay (average days) | 2.4 | 2.4 | 2.4 | p = 1.0 | - |
Gestational age at birth (completed weeks) | Â | Â | Â | Â | Â |
 <37 | 136 (6.8) | 61 (6.6) | 75 (7.0) | p = 0.8 | 0.96 (0.67–1.36) |
 ≥37 | 1853 (93.2) | 852 (93.4) | 1001 (93.1) |  | Reference |
Infant gender | Â | Â | Â | Â | Â |
 Male | 1024 (51.5) | 456 (50.0) | 568 (52.8) | p = 0.2 | 0.89 (0.75–1.07) |
 Female | 965 (48.5) | 457 (50.1) | 508 (47.2) |  | Reference |
Infant admission to intensive care or special care nursery | 324 (16.4) | 132 (14.6) | 192 (18.0) | p = 0.04 | 0.78 (0.61–0.99) |