Scenario‐Based Guidance for International Growth Standards ( GIGS ): For Whom, When, and How to Apply the INTERGROWTH ‐21st and WHO Child Growth Standards

OBJECTIVE: To demonstrate when, for whom, and how to apply the INTERGROWTH-21st (IG-21st) and WHO Child Growth Standards (WHO GS) using a scenario-based approach with illustrations utilising a sub-set of data from a multi-country low birthweight infant prospective cohort. DESIGN: Scenario-based methodological study illustrating application of existing international growth standards. SETTING: Global; applicable across public health, clinical, research, and epidemiological contexts where child growth monitoring is key. POPULATION OR SAMPLE: Neonates and children under 5 years. METHODS: Scenario-based analyses were illustrated using a sub-set of data from the Low birthweight Infant Feeding Exploration (LIFE) study. Weight-for-age z-scores (WAZ) were computed and compared across two existing international growth standards for illustration. MAIN OUTCOME MEASURES: Differences in infant growth assessment outcomes when applying WHO GS and IG-21st, including effects of gestational age correction, are demonstrated through WAZ trajectories and classification differences across preterm and term infants. RESULTS: Scenario-based analyses showed that applying growth standards inappropriately can substantially misclassify infant growth. The GIGS-recommended approach, using IG-21st at birth and for preterm growth, and WHO GS for term and later postnatal growth, provides consistent and accurate assessment. CONCLUSION: The scenario-based analysis presented in this paper illustrates how growth assessment outcomes can vary depending on the standard used, highlighting the importance of selecting the appropriate growth chart based on gestational age or age at measurement and targeted population. This guidance promotes standardised application of existing international growth standards in research and programmatic settings to facilitate resource allocation and tracking towards global nutrition targets.