A new international growth reference is being prepared based on children who are fed according to World Health Organization recommendations, which entail exclusive breast-feeding for the first 4-6 mo of life. However, the number of exclusively breast-fed infants in most societies is small, so that selection biases may result from using such a population. We examined the variability in linear and soft tissue growth of infants according to their feeding patterns, emphasizing differences between exclusively and predominantly (breast milk plus fluids) breast-fed infants. About 650 infants from a relatively developed urban area in southern Brazil were examined at the ages of 1, 3, 6, and 12 mo, and an additional 800 infants at 6 and 12 mo. At each visit, infants were weighed and measured and a 24-h dietary recall was completed with the infants' caretakers. In the analyses of growth, care was taken to address the biases of reverse causality, regression to the mean, and confounding. There was little association between feeding pattern and growth in the first month. From 1 to 3 mo, partially breast-fed infants tended to gain more weight, followed by those who were completely weaned. From 3 to 6 mo, fully weaned infants grew fastest in weight and length and exclusively breast-fed infants grew slowest. After 6 mo of age, the growth in length of partially breast-fed and fully weaned infants was similar, but the latter gained more weight. There were virtually no differences between exclusively and predominantly breast-fed infants in the first 6 mo of life. There results suggest that both of these groups may be pooled for the purpose of constructing growth references.
PIP: Under the auspices of the World Health Organization, a new international growth reference is being developed to reflect the growth of breast-fed infants and their tendency to falter from 3-4 months onward. Of concern, however, is the small number of exclusively breast-fed infants in most societies and the potential for selection bias. A study conducted in Brazil in 1993 found no significant differences between exclusively and predominantly breast-fed infants in the first 6 months of life, suggesting that both these groups can be pooled for the purpose of growth reference construction. 650 infants from a relatively developed urban area in southern Brazil (Pelotas) were examined at 1, 3, 6, and 12 months of age and an additional 800 infants were enrolled at 6 and 12 months. There was little association between growth and feeding pattern in the first month of life. Slower growth in the first month increased the risk of subsequent weaning. From months 1-3, partially breast-fed infants tended to gain more weight, followed by those who were completely weaned. During months 3-6, fully weaned infants grew fastest in terms of both weight and length and exclusively breast-fed infants grew slowest. After 6 months of age, the growth in length of partially breast-fed and fully weaned infants was similar, but the latter group gained more weight. The tendency for breast-fed infants to grow more slowly should be considered in view of the many benefits of breast feeding, including protection against infections and diseases of the immune system, psychological advantages, and birth spacing.