Characteristics | Surgery | No surgery | Statistics (mean difference or OR (95% CI)) |
Survivors to 8 years, n | 171 | 375 | |
Fully assessed at 8 years, n (% survivors) | 158 (92) | 341 (91) | |
Perinatal variables | |||
Mother’s age when child born (years), mean (SD) | 29.3 (6.1) | 29.6 (5.7) | −0.1 (−1.0 to 0.7)‡, p=0.78 |
Outborn,† n (%) | 19 (11%) | 30 (8%) | 1.47 (0.82 to 2.63)§, p=0.19 |
Antenatal corticosteroids, n (%) | 139 (81%) | 300 (80%) | 1.04 (0.69, 1.58)§, p=0.84 |
Multiple birth, n (%) | 45 (26%) | 95 (25%) | 1.05 (0.70 to 1.59)§, p=0.81 |
Gestational age at birth (weeks), mean (SD) | 25.3 (1.2) | 26.0 (1.1) | −0.6 (−0.8 to 0.4)‡, p<0.001 |
Birth weight (grams), mean (SD) | 815 (172) | 888 (185) | −66 (−98 to 34)‡, p<0.001 |
Birth weight (z-score), mean (SD) | −0.41 (0.81) | −0.33 (0.88) | −0.04 (−0.19 to 0.11)‡, p=0.58 |
Male, n (%) | 110 (64%) | 171 (46%) | 2.29 (1.56 to 3.35)§, p<0.001 |
Exogenous surfactant, n (%) | 133 (78%) | 239 (64%) | 1.92 (1.28 to 2.89)§, p=0.002 |
Patent ductus arteriosus, n (%) | 126 (74%) | 217 (58%) | 1.99 (1.34 to 2.95)§, p=0.001 |
Grade 3 or 4 intraventricular haemorrhage, n (%) | 18 (11%) | 20 (5%) | 2.08 (1.08 to 4.04)§, p=0.03 |
Cystic periventricular leucomalacia, n (%) | 16 (10%) | 11 (3%) | 3.72 (1.65 to 8.39)§, p=0.002 |
Necrotising enterocolitis, n (%) | 30 (19%) | 13 (3%) | 5.92 (3.00 to 11.7)§, p<0.001 |
Postnatal corticosteroids, n (%) | 94 (58%) | 106 (28%) | 3.94 (2.66 to 5.83)§, p<0.001 |
In oxygen at 36 weeks’ postmenstrual age, n (%) | 111 (69%) | 154/384 (40%) | 3.39 (2.32 to 4.97)§, p<0.001 |
Corrected* age at assessment (years), mean (SD) | 8.23 (0.56) | 8.37 (0.57) | −0.08 (−0.19 to 0.02)‡, p=0.10 |
Social variables (for those fully assessed) | |||
Lower maternal education, n (%) | 64/155 (41%) | 178/337 (53%) | 1.06 (0.72 to 1.56)§, p=0.76 |
Lower social class, n (%) | 60/151 (40%) | 99/333 (30%) | 1.24 (0.97 to 1.58)§, p=0.09 |
Multilingual family, n (%) | 25/157 (16%) | 69/339 (20%) | 0.76 (0.50 to 1.16)§, p=0.20 |
*Corrected for prematurity.
†Born outside a tertiary maternity hospital.
‡Mean difference (95% CI), adjusted for clustering of multiples using generalised estimating equations (GEEs).
§OR (95% CI), adjusted for clustering of multiples using GEEs.