Effect of Prolonged and Exclusive Breast Feeding on Risk of Allergy and Asthma : Cluster Randomized Trial

The question of whether breast-feeding protects against allergy and asthma has yet to be definitively answered. This cluster randomized trial, carried out at 31 maternity centers in Belarus, enrolled 17,046 mother-infant pairs, 81.5% of which were followed up to age 6.5 years. They were randomly assigned to usual practice or to an intervention promoting breast-feeding that is modeled on the WHO/UNICEF baby-friendly hospital initiative. The intervention is designed to promote and support beast feeding, especially in mothers who have elected to begin breast-feeding. The major outcomes were responses to the International Study of Asthma and Allergies in Childhood questionnaire and the results of skin prick tests of 5 inhaled antigens. The randomized groups were similar with regard to baseline sociodemographic and clinical variables. The rate of exclusive breast-feeding at age 3 months was much higher in the intervention group than in control women (44.3% vs. 6.4%). The prevalence of any degree of breast-feeding was significantly higher in the intervention group at all ages up to-and including-12 months. The intervention, however, did not appear to lessen the risk of allergic symptoms or diagnoses, or the frequency of positive skin prick tests. After eliminating 3 experimental and 3 control sites with suspiciously high rates of positive skin prick tests, the rate of positive skin prick tests for 4 of the 5 antigens was significantly increased in the intervention group. These findings fail to support a protective effect of prolonged or exclusive breast-feeding against asthma, hay fever, or eczema at age 6.5 years. The intervention also failed to lower the prevalence of positive skin prick tests. One must look elsewhere to explain the recent "epidemic" of allergy and asthma.