Clinical characteristics and outcomes as stratified by study epoch
| Epoch 1 (n=18 316) | Epoch 2 (n=20 146) | Epoch 3 (n=21 606) | |
| Mean maternal age (SD) | 28.1 (7.5) | 29.4 (6.4) | 29.6 (6.7)* |
| Maternal ethnicity (%) | |||
| Indigenous† | 1940 (10.6) | 2506 (12.4) | 2725 (12.6)* |
| Asian | 978 (5.3) | 1211 (6.0) | 1940 (9.0)* |
| Caucasian | 12 622 (68.9) | 14 176 (70.4) | 14 531 (67.3)* |
| Other | 211 (1.2) | 287 (1.4) | 515 (2.4)* |
| Assisted conception (%) | 1561 (12.0) | 2412 (13.4) | 2317 (11.3)* |
| Multiple gestation (%) | 4975 (27.2) | 6009 (29.8) | 5998 (27.8)* |
| Vaginal birth (%) | 7655 (42.5) | 7667 (38.1) | 8255 (38.4)* |
| PROM>24 hours (%) | 3520 (21.1) | 4374 (21.8) | 4644 (23.7)* |
| PTL (%) | 11 539 (63.5) | 12 411 (61.7) | 12 206 (56.6)* |
| PIH (%) | 3536 (20.4) | 3303 (16.4) | 3222 (15.0)* |
| APH (%) | 4032 (24.2) | 4341 (21.6) | 4630 (21.5)* |
| Antenatal steroids (%) | 14 297 (82.6) | 16 882 (86.7) | 19 014 (89.4)* |
| GA ≤27 weeks (%) | 5972 (32.6) | 6313 (31.3) | 6762 (31.3)* |
| Mean GA, weeks (SD) | 28.4 (2.2) | 28.5 (2.2) | 28.5 (2.2)* |
| Mean birth weight, g (SD) | 1202 (387) | 1223 (393) | 1238 (396)* |
| SGA (%) | 558 (3.0) | 577 (2.9) | 608 (2.8) |
| Outborn (%) | 1992 (11.4) | 2635 (13.1) | 2923 (13.6)* |
| Male (%) | 9987 (54.6) | 10 923 (54.3) | 11 772 (54.5) |
| Apgar score <7 at 5 min (%) | 2807 (15.3) | 2732 (13.6) | 4182 (19.4)* |
| Intubated at birth (%) | 9387 (52.6) | 7835 (38.9) | 8666 (40.2)* |
| Surfactant (%) | 10 010 (55.4) | 10 056 (50.4) | 12 121 (56.3)* |
| Sepsis (%) | 4893 (27.2) | 3016 (20.2) | 2221 (16.8)* |
| Severe IVH (%) | 1113 (6.6) | 1051 (5.7) | 987 (5.0)* |
| Death (%) | 1963 (10.7) | 1876 (9.3) | 1687 (7.8)* |
| Death and/or severe IVH (%) | 2586 (14.1) | 2433 (12.1) | 2204 (10.2)* |
| Major morbidity‡ | 3618 (19.8) | 5454 (27.1) | 5570 (25.8) |
*P<0.01 for comparison between three epochs.
†Includes person of Aboriginal or Torres Strait Islander descent, Pacific Islander background or Maori.
‡Having any one or more of: severe IVH, NEC stage 2 or higher, BPD, stage 3 or higher ROP.
APH, antepartum haemorrhage; BPD, bronchopulmonary dysplasia; GA, gestational age; IVH, intraventricular haemorrhage; NEC, necrotising enterocolitis; PIH, pregnancy-induced hypertension; PROM, prolonged rupture of membrane; PTL, preterm labour; ROP, retinopathy of prematurity; SGA, small for gestational age.