Introduction

The investigators are: Professor Michael Kramer, McGill University, Canada; Professor Richard Martin; University of Bristol, UK and Dr Emily Oken, Harvard University, USA.

We are indebted to our collaborators in Belarus based in the National Research and Applied Medicine Centre 'Mother and Child', Minsk and all the pediatricians involved in this study; the Department of Maternal and Child Health at the Ministry of Health in Minsk, who have collaborated in all phases of PROBIT and all the children and parents who have made this study possible.

Background

The aim of PROBIT is to investigate the influence of breastfeeding on health outcomes within the setting of a randomised controlled trial in which the randomised arms differ substantially with respect to the duration and exclusivity of breastfeeding.

To date the overwhelming majority of research in this area has been based on animal models or observational cohort studies. The relevance of the former research to humans is unclear, whilst criticism of the latter studies centres around selection bias and uncontrolled confounding.

It is likely that the effects of breastfeeding can only be convincingly demonstrated in large, randomised controlled trials, but it is not possible to randomise healthy term-infants to breastfeeding versus formula feeding. It is possible, however, to randomise to a breastfeeding promotion intervention.

PROBIT I

In PROBIT I (Principal Investigator: Professor Michael Kramer, McGill University), 31 maternity hospitals and one of the polyclinics (the clinics where children are followed for routine health care) affiliated with each maternity hospital were randomised to receive a breastfeeding promotion intervention modelled on the WHO/UNICEF Baby-Friendly Hospital Initiative or to continue the maternity hospital and polyclinic practices in effect at the time of randomisation.

A total of 17,046 subjects were recruited from the 31 randomised sites, with only 555 (3.3%) lost to follow-up at 12 months. Because all infants were initially breastfed, the experimental intervention was designed to increase the duration and exclusivity of breastfeeding.

PROBIT II

In PROBIT II, (Principal Investigator: Professor Michael Kramer, McGill University) further follow-up of the trial participants at age 6½ years, succeeded in evaluating 13,889 children, i.e., 84% of those children still participating at 12 months. Data collection included measurement of atopy, cognitive development, behaviour, growth, obesity, and blood pressure.

PROBIT III

PROBIT III (Principal investigators: Professor Michael Kramer, McGill University , Professor Richard Martin, University of Bristol, and Dr Emily Oken, Harvard University ) at age 11 ½ years , measured growth, obesity, blood pressure, capillary blood glucose using a glucometer and obtained filter paper blood spots after an overnight fast to measure insulin and other markers of chronic disease risk.

PROBIT IV

The current phase, PROBIT IV at age 15½ years (Principal investigators: Professor Michael Kramer, McGill University, Professor Richard Martin, University of Bristol, and Dr Emily Oken, Harvard University ) will examine growth, obesity, blood pressure , neurocognitive function, vision, eczema and lung function. Collaborators for PROBIT IV include: Dr Carsten Flohr (UK), Dr John Henderson (UK), Dr Chris Owen (UK), Dr Seungmi Yang (Canada), Dr Konstatin Vilchuck (Belarus) and Dr Natalia Bogdanovich (Belarus). Study coordinators are Rita Patel (UK) and Bonnie Andrews (USA).