| Number of events(chronic asthma) | HR | Adjusted* HR (95% CI) | p Value | |
| All | 11.1 (348) | 1.89 | 1.77 (1.29 to 2.43) | <0.001 |
| Non-allergic parents | 8.3 (124) | 1.54 | 1.30 (0.74 to 2.28) | 0.36 |
| Only one allergic parent | 14.5 (168) | 1.87 | 1.81 (1.14 to 2.88) | 0.01 |
| Two allergic parents | 21.1 (56) | 3.01 | 2.72 (1.28 to 5.78) | 0.01 |
The hazard ratio (HR) is for the children born by caesarean section compared with children born by vaginal delivery.
*Adjusted for gender, birth weight, breastfeeding, maternal education and maternal body mass index (and for parental allergy status in the analysis of the total study population).