| Birth weight ⩾90th percentile | Birth length ⩾90th percentile | |||
| % | Crude OR (95% CI) | % | Crude OR (95% CI) | |
| Body mass index (BMI) at age 4 | ||||
| 10th to 90th percentile | 10.8 | 1.0 | 16.9 | 1.0 |
| ⩾90th percentile | 21.5 | 2.25 (1.62 to 3.12) | 17.1 | 1.02 (0.72 to 1.45) |
| Family history of allergy | ||||
| No | 11.0 | 1.0 | 16.1 | 1.0 |
| Yes | 11.8 | 1.08 (0.84 to 1.38) | 17.1 | 1.08 (0.87 to 1.33) |
| Young maternal age (⩽25 years) | ||||
| No | 11.2 | 1.0 | 16.5 | 1.0 |
| Yes | 12.7 | 1.15 (0.74 to 1.79) | 16.0 | 0.97 (0.64 to 1.45) |
| Sex | ||||
| Girl | 8.9 | 1.0 | 12.4 | 1.0 |
| Boy | 13.6 | 1.60 (1.25 to 2.06) | 20.2 | 1.79 (1.44 to 2.22) |
| Exclusive breastfeeding (⩾4 months) | ||||
| No | 11.5 | 1.0 | 15.1 | 1.0 |
| Yes | 11.3 | 0.98 (0.71 to 1.35) | 16.8 | 1.13 (0.85 to 1.51) |
| ⩾1 older sibling | ||||
| No | 9.3 | 1.0 | 15.5 | 1.0 |
| Yes | 14.0 | 1.59 (1.25 to 2.03) | 17.8 | 1.18 (0.95 to 1.46) |
| Gestational age | ||||
| 36 to 42 weeks | 11.0 | 1.0 | 16.3 | 1.0 |
| >42 weeks | 22.9 | 2.40 (1.42 to 4.07) | 24.4 | 1.65 (0.99 to 2.77) |
| Maternal perinatal smoking | ||||
| No | 11.7 | 1.0 | 16.9 | 1.0 |
| Yes | 8.3 | 0.68 (0.45 to 1.03) | 12.9 | 0.73 (0.51 to 1.03) |
| Socio-economic index | ||||
| Blue-collar | 10.3 | 1.0 | 14.3 | 1.0 |
| White-collar (low and intermediate level) | 12.3 | 1.22 (0.86 to 1.73) | 17.5 | 1.27 (0.93 to 1.74) |
| White-collar (high level) | 10.7 | 1.04 (0.72 to 1.51) | 16.3 | 1.16 (0.84 to 1.61) |
10th percentile<birth weight<90th percentile and 10th percentile<birth length<90th percentile served as reference groups. CI, confidence interval; OR, odds ratio. Family history of allergy: doctor diagnosed asthma with asthma medication and/or rhinitis and/or pet or pollen allergy in at least one of the parents. Maternal perinatal smoking: maternal smoking during pregnancy and/or during the first 2 months of life of the child. Socio-economic index: classified according to the Nordic standard occupational classification and the Swedish socio-economic classification. The children were categorised on the basis of their parents’ occupation into unskilled and skilled blue-collar workers including students and unemployed (as the reference category), low and intermediate level white-collar workers, and high level white-collar workers.