Are Pregnant Women Vulnerable in Heat Waves?

Investigators performed a systematic review and meta-analysis of studies on the association between environmental temperature and birth outcomes. Exposures were defined as heat waves (2 days of temperatures above the 90th percentile), incremental increases of 1°C, and various absolute temperature thresholds.

In a meta-analysis of six studies, the odds of preterm birth were 1.16-fold greater during a heat wave than on non–heat wave days, 1.05-fold greater per 1°C rise in temperature, and 1.14-fold greater with exposure to elevated temperatures during one trimester or the entire pregnancy. Most studies reported a dose-response relation between rates of preterm birth and increasing temperatures or longer duration of elevated temperature. In 16 …