Table 1

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)*
 Asian978 (5.3)1211 (6.0)1940 (9.0)*
 Caucasian12 622 (68.9)14 176 (70.4)14 531 (67.3)*
 Other211 (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.