Fetal growth in chronic hypoxia: birth weight percentile curves at high altitude

Abstract

Introduction: Currently used birth growth charts are not 
suitable for newborns in high-altitude areas. This study aims to propose weight charts for newborns born at high altitudes. 
Methods: This was a retrospective, cross-sectional study 
based on anthropometric data from 30,756 newborns born between January 2012 and December 2024 in a hospital located at 3,250 meters above sea level. Newborns were included from 28 to 42 weeks, with birth weight recorded within the first 24 hours of life. The 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles of birth weight were calculated using quantile regression models by sex and gestational age. The goodness of fit of the models was assessed using the Akaike information 
criterion and the Kolmogorov-Smirnov test, and finally compared with the INTERGROWTH-21st charts. 
Results: Birth weight percentiles between sexes did not 
show significant differences until after 37 weeks, with higher average weights in males, the highest being +150 g at 42 weeks. When compared with INTERGROWTH-21st, lower weights were evident for both sexes. Conclusions: The percentile curves obtained suggest that, for a more accurate assessment of fetal growth and identification of at-risk newborns in high-altitude populations, it is advisable to use separate charts, due to differences in intrauterine growth resulting from a chronic hypobaric hypoxia environment.