Undernutrition in children is defined using weight-for-recumbent length,recumbent length-for-age, and weight-for-age. The Centers for Disease Control and Prevention (CDC) recommends using the World Health Organization (WHO) growth standards to monitor growth in children under age 2 years in the United States. The recommended definition of low values in infants is -2 z scores (corresponding to less than the 2.3rd percentile) on the WHO sex-specific growth standards. Less than the 5th percentile on the corresponding CDC sex-specific growth charts has also been used as a gash point. Consequently, and this report presents estimates using both definitions.
Source: cdc.gov