Temperature and congenital birth disorders: Evidence from Mexico

This paper tests whether high ambient temperatures during pregnancy - a channel proposed by medical researchers and biologists - help explain the onset of congenital birth disorders (CBDs). Our analysis leverages administrative data on approximately 15 million births across 56,000 localities in Mexico between 2008 and 2021 which we combine with high-resolution temperature data. Leveraging a high-dimensional fixed-effects model at the administrative level-3 (locality), we isolate the causal effect of in-utero temperature exposure on CBD incidence. Overall, we find evidence in support of the view that high ambient temperatures induce CBDs. Our results suggest that an average increase of 1 °C during pregnancy leads to a rise in CBDs by 0.013ppt (1.3 percent). The effects are concentrated in early gestation (first pregnancy trimester), consistent with medical evidence on critical periods of fetal development.