Objective To analyze the changes in birth weight among 27 025 newborns at Luohu District, Shenzhen from 2011 to 2020 and explore the factors associated with it.

Methods The data of this study collected from the Maternal and Child Information Management System in Shenzhen, Guangdong Province. Pregnant women who gave birth at Shenzhen Luohu People's Hospital from January 2011 to December 2020 and their newborns with complete medical records were recruited as research subjects. Kruskal-Wallis test, one-way ANOVA, and two-sample t-test were used to analyze differences of newborn birth weights between various groups with different maternal and infant characteristics. Chi-squared tests were used to explore the trend of low birth weight and macrosomia incidence at Luohu District, Shenzhen from 2011 to 2020. Mann-Kendall trend test was used to analyze the changing trends of newborn birth weight, and logistic regression analysis was used to explore the factors associated with low birth weight and macrosomia.

Results The average birth weight of the 27 025 newborns was (3 260.3 ± 446.9) g. The rate of low birth weight was 4.44%, and that of macrosomia was 3.67%. The average birth weight of newborns showed a downward trend 2011 - 2020 (Z = - 2.5, P_trend = 0.01). Newborns in groups characterized by male gender, older gestational age, singleton, non-Guangdong household registration, older maternal age, cesarean section delivery, and multiparity had higher birth weights (all P < 0.05).

Conclusion The birth weight of newborns has showed a downward trend from 2011 to 2020 at Luohu District, Shenzhen, and the incidence of low birth weight is increasing year by year. This issue should capture further attention.