BMJ  2007;335:815 (20 October), doi:10.1136/bmj.39304.464016.AE (published 11 September 2007)

Research

Effect of prolonged and exclusive breast feeding on risk of allergy and asthma: cluster randomised trial

¹ Departments of Pediatrics and of Epidemiology and Biostatistics, McGill University Faculty of Medicine; and Institute of Human Development and Child and Youth Health, Canadian Institutes of Health Research (CIHR), Montreal, Canada, ² Maternal and Child Health Department, Belarussian Ministry of Health, ³ Belarussian Maternal and Child Health Research Institute, ⁴ Departments of Pediatrics and of Epidemiology and Biostatistics, McGill University; and IS/IT, McGill University Health Centre Research Institute, Montreal, ⁵ Department of Pediatrics, McGill University; and Division of Pediatric Allergy and Clinical Immunology, Montreal Children's Hospital, McGill University Health Centre

Objective To assess whether exclusive and prolonged breast feeding reduces the risk of childhood asthma and allergy by age 6.5 years.

Design Cluster randomised trial.

Setting 31 Belarussian maternity hospitals and their affiliated polyclinics.

Participants A total of 17 046 mother-infant pairs were enrolled, of whom 13 889 (81.5%) were followed up at age 6.5 years.

Intervention Breastfeeding promotion intervention modelled on the WHO/UNICEF baby friendly hospital initiative.

Main outcome measures International study of asthma and allergies in childhood (ISAAC) questionnaire and skin prick tests of five inhalant antigens.

Results The experimental intervention led to a large increase in exclusive breast feeding at 3 months (44.3% v 6.4%; P<0.001) and a significantly higher prevalence of any breast feeding at all ages up to and including 12 months. The experimental group had no reduction in risks of allergic symptoms and diagnoses or positive skin prick tests. In fact, after exclusion of six sites (three experimental and three control) with suspiciously high rates of positive skin prick tests, risks were significantly increased in the experimental group for four of the five antigens.

Conclusions These results do not support a protective effect of prolonged and exclusive breast feeding on asthma or allergy.

Trial registration Current Controlled Trials ISRCTN37687716 [controlled-trials.com] .

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