From the Atacama to Patagonia: Understanding the Effects of Extreme Temperatures on Birth Weight Across Climate Regions in Chile

Exposure to extreme temperatures during pregnancy can have adverse effects on birth weight, however, there is little evidence from Latin America. We used birth records in 2011-2020. Mean, minimum, and maximum daily temperatures were obtained from meteorological stations in 26 municipalities representing different climatic zones of Chile. We explored different windows of exposure (entire pregnancy, trimester, and gestational week) and calculated temperature percentiles based on climatic zone for each window. The 50th percentile served as the reference for comparison. General additive models and distributed lag nonlinear models (DLNM) adjusted for month and year of last menstrual cycle, maternal and paternal: age, education, and employment. Exposure to cold mean temperatures (≤10th percentile) in the total pregnancy period and each trimester was associated with a lower mean birth weight (-28.7 g for the total period, -45.9, -36.1, and -83.4 g for trimester 1, 2, and 3, respectively), whereas exposure to warm mean temperatures was associated with higher birth weight (21.3 g for >90th percentile). For extreme temperatures, exposure to both cold (≤10th percentile for minimum) and hot (>90th percentile for maximum) in the total pregnancy period related to lower birth weight: -48.7 g (95% CI -49.7; -47.6) and -17.48 g (95% CI -18.5; -16.4), respectively, with similar effects by trimester. In DLNM, consistent effects were observed later in pregnancy. Lower birthweight was observed with exposure to extreme cold and heat, while warmer mean temperatures were associated with higher birthweight. Findings from Chile underscore regional impacts of climate change on child health.