Anthropometric indices and exclusive breastfeeding in the first six months of life: a comparison with reference standards NCHS, 1977 and WHO, 2006.

Background: There is a gap in knowledge on the growth of children exclusively breastfed during the fifth and sixth months of life. This study aimed to assess the growth of infants who were exclusively breastfed for the first 6 months of life and compare the distributions of anthropometric measures based on the National Center for Health Statistics (NCHS, 1977) and World Health Organization (WHO, 2006) curves.
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.