Perinatal data and 8-year characteristics of the cohorts with utility data at 8 years of age
| Era of birth | ||||||
| 1991–92 | 1997 | 2005 | ||||
| EP | Control | EP | Control | EP | Control | |
| Utility data available—n | 196 | 214 | 135 | 169 | 144 | 187 |
| Perinatal data | ||||||
| Antenatal corticosteroids | 141 (72%) | 1 (0.5%) | 121 (90%) | 2 (1.2%) | 124 (86%) | 1 (0.5%) |
| Multiple birth | 67 (34%) | 2 (0.9%) | 25 (19%) | 1 (0.6%) | 35 (24%) | 0 (0%) |
| Caesarean birth | 50 (26%) | 25 (12%) | 74 (55%) | 46 (27%) | 82 (57%) | 55 (29%) |
| Birth weight (g) | 892 (173) | 3422 (439) | 825 (180) | 3504 (455) | 869 (193) | 3592 (484) |
| Gestational age (weeks) | 25.8 (1.1) | 39.4 (1.3) | 25.6 (1.2) | 39.3 (1.1) | 25.8 (1.2) | 39.5 (1.3) |
| Male | 100 (51%) | 99 (46%) | 73 (54%) | 91 (54%) | 69 (48%) | 84 (45%) |
| Birth weight z-score | −0.23 (0.87) | −0.02 (0.89) | −0.52 (0.86) | 0.16 (0.90) | −0.29 (0.85) | 0.27 (0.91) |
| Oxygen dependence at 36 weeks | 90 (46%) | NA | 54 (40%) | NA | 83 (58%) | NA |
| Postnatal corticosteroids | 80 (41%) | NA | 66 (44%) | NA | 31 (22%) | NA |
| Grade 3 or 4 intraventricular haemorrhage | 17 (9%) | NA | 5 (4%) | NA | 11 (8%) | NA |
| Cystic periventricular leukomalacia | 13 (7%) | NA | 5 (4%) | NA | 4 (3%) | NA |
| Surgery during the primary hospitalisation | 54 (28%) | NA | 40 (30%) | NA | 44 (31%) | NA |
| 8-year data | ||||||
| Corrected age assessed (years) | 8.7 (0.3) | 8.9 (0.4) | 8.5 (0.4) | 8.5 (0.3) | 7.7 (0.4) | 7.7 (0.5) |
| IQ <−2 SD | 27/195 (14%) | 6/208 (3%) | 11/133 (8%) | 2/167 (1.2%) | 18/143 (13%) | 0/186 (0%) |
| Cerebral palsy | 25 (13%) | 1/212 (0.5%) | 14/133 (11%) | 0/168 (0%) | 18/143 (13%) | 0 (0%) |
| Blind | 2 (1.0%) | 0/212 (0%) | 2 (1.5%) | 0 (0%) | 0/141 (0%) | 0/186 (0%) |
| Deaf | 3 (1.5%) | 0/212 (0%) | 2 (1.5%) | 0 (0%) | 5/143 (3.5%) | 1/185 (0.5%) |
| Lower maternal education | 98/194 (51%) | 78/212 (37%) | 69 (51%) | 49/168 (29%) | 63/143 (44%) | 39/186 (21%) |
| Lower social class | 65/194 (34%) | 41 (19%) | 35 (28%) | 26/161 (16%) | 50 (35%) | 20 (11%) |
Data are n (%), or mean (SD).
EP, extremely preterm; NA, not available.