Wright et al 1 found an increased risk for asthma and wheeze in breastfed children whose mothers had asthma themselves. Data on 9644 children aged 5–6 years from the Bavarian farmers' study2 allowed us to test whether this somewhat unexpected finding is reproducible in a different setting.

Lifetime prevalence of doctor diagnosed asthma (physicians' diagnosis of “asthma” at least once or asthmatic, spastic, or obstructive bronchitis more than once) and symptoms of asthma (wheeze ever, ISAAC core questions) were the main outcome measures of our investigation. Odds ratios for multivariate logistic regression with adjustment for the number of older siblings, parental education, family history of atopic disease other than maternal asthma, and farming are presented.

In children whose mothers had asthma themselves much higher odds ratios for the impact of breast feeding on the risk for doctors' diagnosed asthma were found than in children without maternal asthma (adjusted odds ratio (aOR) 2.37 (95% CI 1.29 to 4.33)v 1.11 (95% CI 0.86 to 1.44); test for homogeneity of odds ratios: χ²=6.209, p=0.013). As in the study by Wright et al, a similar but not significant effect was observed regarding wheezing (aOR for children with maternal asthma 1.32 (95% CI 0.86 to 2.01)v 1.03 (95% CI 0.91 to 1.17) in children whose mothers did not have asthma). In children of mothers with hay fever or eczema, breast feeding was not related to childhood asthma.

Our data confirm an increased and specific risk for doctor diagnosed asthma related to breast feeding in children whose mothers had asthma themselves, emphasising the need for further research on the causes of this association.