Implications for Newborn and Child Growth Classification Using INTERGROWTH‐21st and WHO Child Growth Standards

The application of the WHO GS alone may misclassify preterm and term infants' growth status, particularly at birth and during early infancy. The use of the IG-21st standards provides GA-specific classifications that may more closely align with expected growth patterns in term and preterm infants and could support more accurate monitoring during the first year of life. Based on these implications analyses, we recommend the use of the IG-21st NBS for cross-sectional assessment at birth, the IG-21st PPS from 27 to 64 weeks postmenstrual age, and the WHO GS for all babies thereafter.