Large differences exist in size at birth and in rates of impaired fetal growth worldwide. The relative effects of nutrition, disease, the environment, and genetics on these differences are often debated. In clinical practice, various references are often used to assess fetal growth and newborn size across populations and ethnic origins, whereas international standards for assessing growth in infants and children have been established. In the INTERGROWTH-21st Project, our aim was to assess fetal growth and newborn size in eight geographically defined urban populations in which the health needs of mothers were met and adequate antenatal care was provided.
Through the Fetal Growth Longitudinal Study and Newborn Cross-Sectional Study, data showed that fetal growth and newborn length are similar across diverse georgraphical settings when mothers' nutritional and health needs are met, and environmental constraints on growth are low. The findings for birthlength are in strong agreement with the WHO Multicentre Growth Reference Study (MGRS). These results provide the conceptual frame to create international standards for growth from conception to newborn baby, which will extend the present infant to childhood WHO MGRS standards.