Prevalence of asthma and mean lung function according to level of maternal smoking during pregnancy
| Asthma | FEV1 | FEF25–75 | ||||
| N | Prevalence (%) | N | Mean (SD score) | N | Mean (SD score) | |
| Maternal smoking status | ||||||
| Not exposed | 3720 | 11.3 | 3077 | 0.02 | 3118 | 0.03 |
| Passive only | 2609 | 12.2 | 2163 | 0.00 | 2213 | 0.03 |
| 1–9/day | 656 | 13.6 | 521 | 0.02 | 526 | −0.03 |
| 10–19/day | 721 | 15.0 | 513 | −0.04 | 517 | −0.19 |
| ≥20/day | 296 | 14.5 | 230 | −0.10 | 232 | −0.14 |
FEF25–75, maximal mid expiratory flow; FEV1, forced expiratory volume in 1 s.