The Association between Extreme Temperatures and Birth Weight in South Korea

Abstract This study examined the effect of ambient temperatures in utero on newborn children’s birth weight in South Korea and showed that exposure to high temperatures (over 30°C/85°F) is associated with negative birth outcomes. The impact was observed primarily in the second trimester. Per estimates, one extra day in the second trimester, exposing to more than 30°C, lowers birth weight by 0.8%. The results further indicated a heterogeneous effect of ambient temperature on birth outcomes by household income. The negative effect of hot-temperature exposure was more apparent in the lower 25% household income group than in the upper 75% household income group.