Birthweight Classification in Colombian Newborns: Agreement Between International and Local Growth Charts

Objective: To assess concordance of birthweight classification between a Colombian prenatal growth chart (FECOPEN) and two international postnatal growth charts (Fenton 2013 and INTERGROWTH-21st [IG-21]) and examine the clinical relevance of these classifications using neonatal outcomes. Methods: A concordance study was conducted among newborns delivered in Bogotá, Colombia. Exclusion criteria included absence of prenatal care or third-trimester ultrasound, maternal residence outside Bogotá, and genetic conditions, congenital malformations, or STORCH infections. Prenatal classification was performed during the third trimester using FECOPEN and postnatal classification at birth using Fenton 2013 and IG-21. Concordance was assessed using Lin’s concordance correlation coefficient (CCC) and weighted kappa statistics. Associations between growth classification and neonatal outcomes were explored. Results: A total of 1,694 newborns with gestational age (GA) between 23 and 41 weeks were included. Birthweight percentiles in the study population differed from international charts. Concordance between FECOPEN and postnatal charts was poor (CCC 0.26–0.49), with modest improvement among infants born at <32 weeks of GA. Concordance between IG-21 and Fenton 2013 was high overall (CCC 0.91), decreasing to 0.82 among infants <32 weeks. Small-for-gestational-age (SGA) classification by any chart was significantly associated with abnormal prenatal Doppler findings (χ², p<0.01). Neonatal outcomes among SGA newborns were similar whether classification was concordant across charts or only between postnatal charts. Agreement for large-for-gestational-age (LGA) classification was poor. Conclusions: International postnatal charts showed good concordance but poor agreement with local growth patterns. Misclassification may lead to unnecessary testing or hospitalizations. Locally derived postnatal charts may improve clinical decision-making.