Preterm, Early-Term Birth Rates Increase After Heat Waves

FRIDAY, May 24, 2024 (HealthDay News) — Preterm and early-term birth rates increase after heat waves, according to a study published online May 24 in JAMA Network Open.

Lyndsey A. Darrow, Ph.D., from the University of Nevada School of Public Health in Reno, and colleagues examined changes in daily rates of preterm and early-term birth after heat waves in a cohort study of singleton births using birth records from 1993 to 2017 from the 50 most populated U.S. metropolitan statistical areas (MSAs).

From 1993 to 2017, there were 53,154,816 eligible births; the analyses included 2,153,609 preterm births and 5,795,313 early-term births in the warm season. The researchers observed positive associations for heat waves with daily rates of preterm and early-term births, showing a dose-response association with duration of heat wave and temperatures and a stronger association in the more acute four-day window. The rate ratios for preterm birth and early-term birth were 1.02 and 1.01, respectively, after four consecutive days of mean temperatures exceeding the local 97.5th percentile. The corresponding rate ratios were 1.04 and 1.03 among those who were 29 years of age or younger, had a high school education or less, and belonged to a racial or ethnic minority group, for the same exposure.

“The modest but robust elevated associations were strongest in the four days preceding birth and for longer durations of heat and higher temperatures,” the authors write.

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