Characteristics of gestation groups
| 25–32 weeks gestation | 33–34 weeks gestation | 35–36 weeks gestation | Term | |
| Total liveborn | 185 | 169 | 522 | 13148 |
| Survivors at 1 year | 160 | 165 | 519 | 13117 |
| Had spirometry at 8–9 years | 68 (43%) | 81 (49%) | 248 (48%) | 6308 (48%) |
| Had spirometry at 14–17 years | 43 (27%) | 49 (30%) | 132 (25%) | 4284 (33%) |
| Had spirometry at 8–9 years and 14–17 years | 33 (21%) | 42 (25%) | 111 (21%) | 3613 (28%) |
| Total number in group who had any spirometry | 78 | 88 | 269 | 6979 |
| Male (%) | 48 (62%) | 54 (61%) | 144 (54%) | 3446 (49%) |
| Maternal smoking (%) | 21/74 (28%) | 20/84 (24%) | 49/264 (19%) | 1282/6826 (19%) |
| Manual workers (%) | 27/54 (50%) | 32/77 (42%) | 108/255 (42%) | 2439/6431 (38%) |
| Exclusively breast fed for at least 3 months (%) | 6/75 (8%) | 12/84 (14%) | 25/266 (9%) | 819/6834 (12%) |
| At spirometry at 8–9 years of age | ||||
| Mean (SD) age (years) | 8.7 (0.4) | 8.6 (0.3) | 8.7 (0.3) | 8.6 (0.3) |
| Mean (SD) height (cm) | 130.9 (6.8) | 130.9 (5.3) | 132.8 (5.1) | 132.4 (5.8) |
| Mean (SD) height (z-score) | −0.336 (1.225) | −0.252 (0.945) | 0.036 (0.883) | 0.011 (1.002) |
| Mean (SD) weight (kg) | 28.1 (6.4) | 28.3 (4.2) | 30.4 (6.0) | 30.3 (5.8) |
| Mean (SD) weight (z-score) | −0.439 (1.107) | −0.363 (0.738) | −0.046 (0.988) | −0.033 (0.990) |
| At spirometry at 14–17 years of age | ||||
| Mean (SD) age (years) | 15.5 (0.2) | 15.5 (0.4) | 15.5 (0.3) | 15.5 (0.3) |
| Mean (SD) height (cm) | 166.7 (9.0) | 168.2 (7.6) | 170.0 (8.0) | 169.2 (8.4) |
| Mean (SD) height (z-score) | −0.505 (1.237) | −0.202 (0.972) | 0.028 (0.933) | 0.007 (0.998) |
| Mean (SD) weight (kg) | 56.3 (9.4) | 60.6 (10.3) | 60.6 (11.8) | 61.6 (12.0) |
| Mean weight (z-score, SD) | −0.468 (0.898) | −0.090 (0.840) | −0.101 (1.006) | 0.011 (1.001) |
| For children who had any spirometry | ||||
| Current asthma at 7.6 years of age based on reported doctor-diagnosed asthma ever with symptoms and/or treatment in previous 12 months (%) | 11/52 (21%) | 13/58 (22%) | 22/182 (12%) | 738/5221 (14%) |
| Current asthma at 13.8 years of age based on doctor-diagnosed asthma ever (%) | 13/50 (26%) | 17/57 (30%) | 48/186 (26%) | 1197/5227 (23%) |
Some of the variables reported had missing data but the denominators are given.