Too hot to hold: the effects of high temperatures during pregnancy on birth weight and adult welfare outcomes

Exposure to high temperatures during pregnancy is generally associated with low birth weight---a proxy for endowment. But whether such early life shock is further related to welfare losses in adulthood is still unknown. Utilizing random temperature fluctuations across 123 counties in China, we examine the relationships between high temperatures during pregnancy and birth weight and later outcomes. One standard deviation of high temperature days during pregnancy triggers about 0.17 kilograms loss of birth weight, and further in adulthood 1.63 cm decrease in height and 0.86 years less of schooling. Health and intelligence outcomes are adversely affected as well. The impacts are concentrated in the first and third trimesters. Such effects should become part of the calculations of the costs of global warming. Back-of-the-envelope predictions suggest that at the end of the 21st century newborns on average weigh 54.36-210.44 grams less. And the losses in height and education years are 0.52-2.02 centimeters and 0.26-1.01 years, respectively. We also argue these patterns are more likely consistent with physiological effects than with income effects, because total precipitation and high temperatures in the growing season of one year before birth have no significant effects.