Table 1

Characteristics of the preterm and control groups

VariablePreterm
n=297
Control
n=260
Antenatal corticosteroids216 (73%)3 (1%)
Caesarean delivery113 (38%)31 (12%)
Gestational age (completed weeks)—mean (SD)26.7 (1.9)39.2 (1.4)
Birth weight (g)—mean (SD)888 (161)3386 (438)
Male137 (46%)126 (48%)
Birth weight z-score−0.73 (1.19)−0.02 (0.88)
Exogenous surfactant119 (40%)0 (0%)
Assisted ventilation281 (95%)0 (0%)
Bronchopulmonary dysplasia*121 (41%)0 (0%)
Postnatal corticosteroids97 (33%)0 (0%)
Assessed at 8 years of age†273 (92%)221 (85%)
Spirometry at 8 years240 (81%)208 (80%)
Age of spirometry at 8 years—mean (SD)8.7 (0.3)8.9 (0.4)
Assessed at 18 years of age‡220 (74%)166 (64%)
Spirometry at 18 years209 (70%)154 (58%)
Age of spirometry at 18 years—mean (SD)17.9 (0.8)18.0 (0.8)
Smoking at 18 years§35/205 (17%)21/152 (13%)
Asthma at 18 years§40/189 (21%)27/143 (19%)
  • Data are n (%), unless otherwise specified.

  • *Defined as oxygen or ventilator dependency at 36 weeks.

  • †Of the 24 participants in the EP/ELBW group not assessed at 8 years, 8 were lost to follow-up, 4 were inaccessible, 11 refused and 1 had only a partial assessment. Of the 39 participants in the control group not assessed at 8 years, 22 were lost to follow-up, 4 were inaccessible and 13 refused.

  • ‡Of the 77 participants in the EP/ELBW group not assessed at 18 years, 15 were lost to follow-up, 3 were inaccessible, 40 refused (including 8 with major disability at 8 years) and 19 had miscellaneous reasons (including 11 with major disability at 8 years). Of the 94 participants in the control group not assessed at 18 years, 30 were lost to follow-up, 5 were inaccessible, 54 refused (including 2 with major disability at 8 years) and 5 had miscellaneous reasons (including 2 with major disability at 8 years).

  • §Of those with spirometry data at 18 years.

  • ELBW, extremely low birth weight; EP, extremely preterm.