Trends in birth weight indicators between 2009 and 2021 in two districts in the southern region of the Buenos Aires Metropolitan Area.

Introduction. Birth weight is an indicator of perinatal health that is influenced by social, environmental, and health-related factors. The objective of this study is to analyze changes in birth weight indicators (birth weight, low birth weight, and small for gestational age) between 2009 and 2021, specifically in two municipalities in the southern region of the Buenos Aires Metropolitan Area (AMBA, by its Spanish acronym). Population and methods. We conducted a retrospective observational study using secondary data on live births collected by the Directorate of Health Statistics and Information (DEIS, by its Spanish acronym) of the Ministry of Health. Trends in birth weight, low birth weight (LBW, <2500 g), and small for gestational age (SGA, <10th percentile) were evaluated using joinpoint regression, and associations with maternal age and educational level were analyzed using a mixed-effects model. Results. Based on a database of 141 525 cases, a moderate upward trend in birth weight was observed, which was statistically significant (p < 0.05) in only one municipality. The proportion of cases born with indicators of low birth weight showed a significant reduction over time (p < 0.05), more pronounced for SGA (~4% annually) than for LBW (~1% annually). In addition, a nonlinear association was found between maternal age and birth weight, and a positive association with maternal educational level (p < 0.001). Conclusion. This analysis provides up-to-date information on birth weight indicators and their maternal determinants in two municipalities in the southern part of the AMBA.