Neonatal 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 |
| Total number in group who had any spirometry | 78 | 88 | 269 | 6979 |
| Mean (SD) birth weight of those who had any spirometry (g) | 1437 (439.5) | 2449 (416.8) | 2634 (424.7) | 3478 (476.6) |
| Mean (SD) birth weight of those who had any spirometry (z-score) | 0.051 (1.297) | 0.396 (1.267) | 0.180 (1.066) | 0.117 (0.976) |
| Mean (SD) gestation of those who had any spirometry (weeks) | 29.7 (2.0) | 33.6 (0.5) | 35.7 (0.5) | 39.7 (1.3) |
| Ventilated, n/N (%)* | 59/78 (76) | 15/88 (17) | 2/269 (1) | 12/6979 (0.2) |
| Mean (range) length of time of ventilation (h) | 245 (1–1416) | 77 (9–168) | 15 (8–22) | 107 (1–576) |
| Type of ventilation, n/N (%)† * | ||||
| CPAP | 43/78 (55.1) | 6/88 (6.8) | 2/269 (0.7) | 3/6979 (0.0) |
| Ventilated via ETT | 41/78 (52.6) | 7/88 (8.0) | 0/269 (0) | 11/6979 (0.2) |
| Other | 21/78 (26.9) | 6/88 (6.8) | 1/269 (0.4) | 5/6979 (0.1) |
| Surfactant treatment, n/N (%)* | 35/78 (44.9) | 6/88 (6.8) | 0/269 (0) | 1/6979 (0.01) |
| Received oxygen at any time, n/N (%)* | 66/78 (85) | 31/88 (35) | 16/269 (6) | 45/6979 (0.6) |
| Number (%) receiving oxygen treatment for:* | ||||
| <1 day | 17/78 (21.8) | 13/88 (14.8) | 8/269 (3.0) | 31/6986 (0.4) |
| 2–4 days | 11/78 (14.1) | 8/88 (9.1) | 7/269 (2.6) | 9/6986 (0.1) |
| ≥5 days | 38/78 (48.7) | 10/88 (11.4) | 0/269 (0) | 4/6986 (0.1) |
Some of the variables reported had missing data.
↵* It was assumed the answer was no for children who did not have a neonatal admissions questionnaire completed, hence percentages are calculated based on the total number in the group who had any spirometry, not the number who had neonatal admissions questionnaires completed.
↵† Some children may have received more than one mode of ventilation.
CPAP, continuous positive airway pressure; ETT, endotracheal tube.