Extreme Heat, Birth Outcomes, and Socioeconomic Heterogeneity

We investigate the effect of extreme heat on birth outcomes and how this effect may vary by family socioeconomic status (SES). We create a detailed data set by linking individual-level data on approximately 4 million newborns in Spanish provincial capitals between 1990 and 2016 with precise meteorological data on the temperatures children experienced throughout their gestation. The outcomes are preterm birth, low birth weight, and very low birth weight. Socioeconomic status is assessed using parents' highest occupational level. We find that the incidence of negative birth outcomes increased for children exposed to extreme heat in early gestation. Further, the effect is concentrated mostly among children from a low socioeconomic background. Given the importance of birth outcomes for the next generation's well-being, our results highlight the potential contributions of extreme temperatures to the widening of preexisting socioeconomic inequalities. The forecasted increase in extreme climatic events makes the results of this study concerning, especially for low-SES children.