An updated reference for age-sex-specific birth weight percentiles stratified for ethnicity based on data from all live birth infants between 2005 and 2014 in Alberta, Canada

Objective This study aims to update the current reference for sex-specific birth weight percentiles by gestational age, overall and for specific ethnic groups, based on data from all singleton live-birth deliveries from 2005 to 2014 in Alberta, Canada. Methods Infant and maternal information were captured in the Alberta Vital Statistics-Births Database for 473,115 singleton infants born to 311,800 women between January 1, 2005 and December 31, 2014. Within each sex, and each sex-ethnic group, birth weights were modelled by gestational age using generalized additive models and natural cubic splines. Crude and corrected estimates for birth weight percentiles including cut-off values for large for gestational age (LGA) and small for gestational age (SGA) were calculated by sex and sex-ethnic group, and gestational age for singleton live births. Results LGA and SGA cut-offs were lower for females than for males for all gestational ages. The SGA and LGA percentiles were greater for both male and female very preterm infants in Alberta compared to previous national references. Ethnicity-specific LGA and SGA cut-offs for term Chinese and preterm and at-term South Asian infants were consistently lower than those for both the general population in Alberta and the previous national reference. South Asian infants had lower birth weights at almost all gestational ages compared with the other groups. Conclusion The updated birth weight percentiles presented in this study highlight the differences in SGA and LGA cut-offs among infants from South Asian, Chinese, and the general population, which may be important for clinical perinatal care.