Comparative analysis of INTERGROWTH-21st and Fenton growth charts for birthweight classification in a multiethnic Asian cohort: a cross-sectional study.

Objective: The objective of this study is to evaluate the impact of using International Fetal and Newborn Growth Consortium for the 21st Century (INTERGROWTH-21st) (IG-21) growth standards compared with Fenton growth charts on birthweight classification in a multiethnic newborn cohort in Singapore.

Design: Cross-sectional study.

Setting: KK Women's and Children's Hospital, Singapore.

Patients: Study population included 2541 babies born between 16 December 2019 and 16 March 2020.

Interventions: None.

Main outcome measures: Birthweight classifications of small for gestational age (SGA), appropriate for gestational age (AGA) and large for gestational age (LGA) were assessed using IG-21 and Fenton growth charts. The level of agreement between the two charts was measured using Cohen's kappa coefficient (K).

Results: Of 2541 neonates, 171 (6.7%) had discordant birthweight classifications. The kappa coefficient indicated moderate overall agreement (K=0.79) between the charts, with decreasing agreement from preterm (K=0.88) to full-term categories (K=0.71). The largest discordance was observed in 98 (60.5%) neonates classified as LGA by IG-21 but AGA by Fenton. In comparison, 60 (2.9%) neonates classified as AGA by IG-21 were SGA by Fenton, while 13 (4.6%) were SGA by IG-21 but AGA by Fenton.

Conclusions: The study found discrepancies in birthweight classification between IG-21 and Fenton growth charts, with Fenton charts overclassifying SGA and underclassifying LGA in our study population. These findings suggest the potential need to integrate IG-21 growth standards into local practice to improve accuracy in neonatal growth assessment. Further research is necessary to evaluate the clinical implications of these discordant classifications on neonatal outcomes.