Table 1– Neonatal characteristics of the two preterm born birth cohorts, by severity of bronchopulmonary dysplasia (BPD)

	Cohort	Non-BPD	Mild BPD	Moderate/severe BPD
Subjects n	1982–85	10	24	12
Subjects n	1991–92	9	14	12
Females	1982–85	5 (50)	11 (46)	5 (42)
Females	1991–92	7 (78)	9 (64)	5 (42)
Gestational age weeks	1982–85	28.3±1.57	27.0±1.29	27.0±1.21
Gestational age weeks	1991–92	28.3±1.41	26.5±1.51	25.8±1.47
Birth weight g	1985–85	1171±149	1013±193	887±126
Birth weight g	1991–92	1053±153	927±208	851±203
Duration of ventilator treatment days	1982–85	0.4 (0.0–4.8)	8.6 (0.8–35.0)	25.4 (0.7–54.0)
Duration of ventilator treatment days	1991–92	0.5 (0–1.7)	3.0 (0–40.0)	12.7 (1.7–54.5)
Postnatal age at room air days	1985–82	12.5 (1.0–25.0)	41.0 (28.0–71.0)	72.5 (55.0–257.0)
Postnatal age at room air days	1991–92	2.0 (2.0–26.0)	45.5 (28.0–70.0)	91.0 (61.0–180.0)
Surfactant treatment	1982–85	0 (0)	0 (0)	0 (0)
Surfactant treatment	1991–92	1 (11)	6 (43)	10 (83)
Antenatal steroid	1982–85	5 (50)	5 (21)	5 (42)
Antenatal steroid	1991–92	3 (33)	8 (57)	4 (33)
Postnatal steroid	1982–85	0 (0)	1 (4)	3 (25)
Postnatal steroid	1991–92	0 (0)	2 (14)	8 (67)

Data are presented as n (% of subgroup), mean±sd or median (range), unless otherwise stated. Mild BPD: need for supplemental oxygen at ≥28 days of postnatal age; Moderate/severe BPD: need for supplemental oxygen at ≥36 weeks of gestational age.