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

BMJ 2007; 335 doi: (Published 18 October 2007) Cite this as: BMJ 2007;335:815
  1. Michael S Kramer, James McGill professor; and scientific director1,
  2. Lidia Matush, chief2,
  3. Irina Vanilovich, senior scientist3,
  4. Robert Platt, associate professor; and investigator and associate director4,
  5. Natalia Bogdanovich, senior scientist3,
  6. Zinaida Sevkovskaya, senior scientist3,
  7. Irina Dzikovich, senior scientist3,
  8. Gyorgy Shishko, director3,
  9. Bruce Mazer, associate professor; and head5
  10. the Promotion of Breastfeeding Intervention Trial (PROBIT) Study Group
  1. 1Departments 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. 2Maternal and Child Health Department, Belarussian Ministry of Health
  3. 3Belarussian Maternal and Child Health Research Institute
  4. 4Departments of Pediatrics and of Epidemiology and Biostatistics, McGill University; and IS/IT, McGill University Health Centre Research Institute, Montreal
  5. 5Department of Pediatrics, McGill University; and Division of Pediatric Allergy and Clinical Immunology, Montreal Children's Hospital, McGill University Health Centre
  1. Correspondence to: M S Kramer, Montreal Children's Hospital, 2300 Tupper Street (Les Tourelles), Montreal, Quebec H3H 1P3 michael.kramer{at}
  • Accepted 27 July 2007


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.


  • MSK is a senior investigator of the Canadian Institutes of Health Research. RP is a Monat-McPherson career investigator of McGill University, and both he and BM are career investigators (chercheurs-boursiers) of the Fonds de la recherche en santé du Québec.

  • Contributors: MSK, RP, and BM contributed to obtaining funding for this project and to the design, analysis, interpretation, writing, and revision of the manuscript. LM, IV, NB, ZS, ID, and GS contributed both to the design of the study and to the planning, implementation, and monitoring of the field work in Belarus. MSK is the guarantor.

  • Funding: Grant (MOP No 53155) from the Canadian Institutes of Health Research. The funder had no role in study design, data collection, data analysis, data interpretation, or writing of this manuscript.

  • Competing interests: None declared.

  • Ethical approval: The research ethics board of the Montreal Children's Hospital of the McGill University Health Centre approved this project (including the 6.5 year follow-up).

    Provenance and peer review: Non-commissioned; externally peer reviewed.

  • Accepted 27 July 2007
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