[WHO growth standards for infants and young children].Arch Pediatr 2009; 16(1):47-53AP
The growth pattern of healthy breastfed infants deviates to a significant extent from the NCHS/WHO international reference. In particular, this reference is inadequate because it is based on predominantly formula-fed infants, as are most national growth charts in use today. The WHO multicentre growth reference study (MGRS), aimed at describing the growth of healthy breastfed infants living in good hygiene conditions, was conducted between 1997 and 2003 in 6 countries from diverse geographical regions: Brazil, Ghana, India, Norway, Oman and the United States. The study combined a longitudinal follow-up of 882 infants from birth to 24 months with a cross-sectional component of 6669 children aged 18-71 months. In the longitudinal follow-up study, mothers and newborns were enrolled at birth and visited at home a total of 21 times at weeks 1, 2, 4 and 6; monthly from 2-12 months; and bimonthly in the 2nd year. The study populations lived in socioeconomic conditions favorable to growth. The individual inclusion criteria for the longitudinal component were: no known health or environmental constraints to growth, mothers willing to follow MGRS feeding recommendations (i.e., exclusive or predominant breastfeeding for at least 4 months, introduction of complementary foods by 6 months of age and continued breastfeeding to at least 12 months of age), no maternal smoking before and after delivery, single-term birth and absence of significant morbidity. Term low-birth-weight infants were not excluded. The eligibility criteria for the cross-sectional component were the same as those for the longitudinal component with the exception of infant feeding practices. A minimum of 3 months of any breastfeeding was required for participants in the study's cross-sectional component. Weight-for-age, length/height-for-age, weight-for-length/height and body mass index-for-age percentile and Z-score values were generated for boys and girls aged 0-60 months. The full set of tables and charts is presented on the WHO website (www.who.int/childgrowth/en), together with tools such as software and training materials that facilitate their application. The WHO child growth standards were derived from children who were raised in environments that minimized constraints to growth, such as poor diets and infection. In addition, their mothers followed healthy practices such as breastfeeding their children and not smoking during and after pregnancy. The standards depict normal human growth under optimal environmental conditions and can be used to assess children everywhere, regardless of ethnicity, socioeconomic status and type of feeding. The standards explicitly identify breastfeeding as the biological norm and establish the breastfed child as the normative model for growth and development. They have the potential to significantly strengthen health policies and public support for breastfeeding. The pooled sample from the 6 participating countries allowed the development of a truly international reference that underscores the fact that child populations grow similarly across the world's major regions when their health and care needs are met. It also provides a tool that is timely and appropriate for the ethnic diversity seen within countries and the evolution toward increasingly multiracial societies in the Americas and Europe as elsewhere in the world. The WHO standards provide a better tool to monitor the rapid and changing rate of growth in early infancy. They also demonstrate that healthy children from around the world who are raised in healthy environments and follow recommended feeding practices have strikingly similar patterns of growth.