Updated Gestational Age Specific Birthweight Reference of Hong Kong Chinese Newborns and Comparison with Local and International Growth Charts

Background: Different gestational age specific birthweight reference charts have been produced for different populations and ethnic groups over different time periods, mostly based on birthweight data. This study aims to update birthweight references for Hong Kong (HK) Chinese newborns to provide norms for identification of small and large for gestational age (SGA and LGA) fetuses, and to verify whether there are significant differences compared to previously published local reference charts, as well as to other southern Chinese and international data. Methods: All singleton Chinese livebirths delivered in United Christian Hospital from 2012 to 2017 were retrospectively included. The smoothed birthweight centiles at each gestation were computed. The birthweight centiles were then compared with other reference charts. Results: A total of 25,508 livebirths between 24 and 42 completed weeks of gestation were enrolled in the final analysis. The mean birthweights of our cohort were largely similar to previous studies at each gestation, but the 10th and 90th centile ranges differed significantly, so that the proportion of babies that would be classified as SGA or LGA varied widely using cut-offs from different studies. Older local studies tend to under-estimate, while the international growth charts would over-estimate the proportion of SGA babies. Conclusions: Updating fetal growth curve references based on local data is essential to establish more precise definitions of SGA and LGA babies in clinical management. The use of international growth charts in our population may not be appropriate and requires further validation.