| Overall | 32 077 (79.3%) |
| Prenatal maternal smoking | |
| No | 26 745 (81.2%) |
| Yes | 3260 (67.0%) |
| Postnatal parental smoking | |
| No | 21 932 (81.8%) |
| Yes | 7903 (73.9%) |
| Sex | |
| Boy | 16 305 (79.2%) |
| Girl | 15 733 (79.5%) |
| Maternal education (years) | |
| ⩽12 | 12 481 (71.1%) |
| >12 to <16 | 13 188 (83.9%) |
| ⩾16 | 5697 (87.2%) |
| Other | 594 (78.8%) |
| Birth weight (g) | |
| <2500 | 1223 (83.3%) |
| 2500–4500 | 29 243 (79.3%) |
| >4500 | 1537 (76.4%) |
| Maternal history of atopy | |
| No | 22 665 (78.5%) |
| Yes | 9412 (81.6%) |
| Season born | |
| Winter | 7534 (79.0%) |
| Spring | 9038 (79.6%) |
| Summer | 7971 (79.2%) |
| Autumn | 7496 (79.4%) |
| Breast feeding (months) | |
| <6 | 5919 (74.3%) |
| ⩾6 | 26 158 (80.5%) |
| Maternal age (years) | |
| <25 | 4001 (72.9%) |
| 25–30 | 14 638 (81.5%) |
| >30 | 13 438 (79.0%) |
| Parity | |
| 0 | 14 448 (84.5%) |
| 1 | 11 329 (78.5%) |
| >1 | 6300 (69.1%) |
| Type of day care | |
| Parent | 9978 (75.5%) |
| Nanny/private home | 10 148 (79.7%) |
| Kindergarten | 11 861 (82.4%) |