Nationwide singleton birth weight percentiles for gestational age in Taiwan in 2008-2017.

Background: Establishing updated, population-based birth weight charts is essential for accurate classification of neonates as small for gestational age (SGA) or large for gestational age (LGA). The current birth weight charts in Taiwan have not been updated for over two decades, and the previous report has found an increasing trend in neonates with low birth weight (LBW) and preterm birth. This study aimed to develop updated birth weight charts and explore trends in LBW and preterm births using nationwide data.

Methods: This study analyzed 1,913,124 singleton live births from the data set of Taiwan Birth Notifications between 2008 and 2017. Birth weight percentiles were calculated for each completed gestational week and gender. A nonlinear, resistant smoothing technique was applied to develop smoothed birth weight-for-gestational-age percentile curves.

Results: The cohort included 994,175 male neonates and 918,949 female neonates. During the study period, the annual mean birth weight decreased significantly from 3098.10g to 3049.88g (p < 0.0001). A significant increase in the annual rate of LBW was observed, rising from 5.59 % in 2008 to 6.98 % in 2017 (p < 0.0001), coinciding with a slight and significant decrease in gestational age (p < 0.001) and a significantly declining proportion of foreign-born mothers (p < 0.0001) during the same period. In addition, birth weight percentiles by weeks of gestation in male and female singleton births were reported.

Conclusion: This study developed an updated, nationwide birth weight chart for Taiwan. An increasing rate of LBW was observed from 2008 to 2017. Further investigation into maternal and environmental factors contributing to these trends is warranted.