Description of the study population, 672children enrolled at birth
| Variable | n | % |
|---|---|---|
| Sex, male | 342 | 50.7 |
| Italian mother | 645 | 95.7 |
| Preterm birth | 37 | 5.5 |
| Small for gestational age | 86 | 12.8 |
| Day-care attendance* | 175 | 26.1 |
| Mother smoking during pregnancy | 82 | 12.2 |
| Breastfeeding at 3 months | 329 | 48.9 |
| Humidity or mould at home | 89 | 13.2 |
| Any pets in home* | 178 | 26.5 |
| Siblings | 283 | 42.1 |
| Mother's education, %high (university degree) | 240 | 35.7 |
| Father's education, %high (university degree) | 192 | 28.6 |
| Mother or father smoking at home* | 90 | 13.4 |
| Mother with asthma | 61 | 9.1 |
| Father with asthma | 67 | 10.0 |
| Mother with chronic bronchitis | 9 | 1.3 |
| Father with chronic bronchitis | 18 | 2.7 |
*From questionnaire at 15 months.