Methods: Cross-sectional study that measured the weight and length of 360 healthy and exclusively breastfed
infants who were enrolled in a primary care program in Belem, Brazil from October 2006 to December 2008. The
children were evenly grouped into age groups from 1 to 6 months of age.
Results: The mean weights were higher than the NCHS, 1977 mean weight for all of the studied groups regardless
of gender and showed greater similarity to the WHO, 2006 mean weight, especially when standard deviations were
considered. Regarding length, although the average length at birth was smaller, females had higher averages in the
second and sixth months compared with the reference curves (p < 0.05).
Conclusions: Exclusive breastfeeding in the first 6 months of life provides adequate physical growth, resulting in
height and weight gain curves that are similar to or greater than the NCHS, 1977 and WHO, 2006 curves. The
greater mean weight at the fifth and sixth months of life suggests that the second-quarter growth curves of children
who are exclusively breastfed are greater than those of children who receive other types of food.