Exposure to hotter air before delivery can result in lower birth weights, shorter pregnancies

Findings were revealed in a new study from Ben-Gurion University of the Negev and Harvard University.

Baby boy in sleeping on bed (photo credit: ING IMAGE/ASAP)
Baby boy in sleeping on bed
(photo credit: ING IMAGE/ASAP)
Babies born in an environment with high temperatures are likely to weigh less and spend less time than normal in their mother’s womb than those exposed to cooler air, according to a new study from Ben-Gurion University of the Negev and Harvard University.
BGU researcher Dr. Itai Kloog of the department of geography and environmental development, and his colleagues from Harvard’s school of public health – Steven J. Melly, Prof. Brent Coull, Dr. Francesco Nordio and Prof. Joel Schwartz – evaluated the possible connection between birth outcomes (especially on birth weight) and ambient air temperature during pregnancy in Massachusetts between 2000 and 2008.
The research does not necessarily involve simple climate but rather the temperature of air resulting from proximity to urban and polluted areas, the lack of open space and road traffic nearby – all of which warm the air, the researchers explained.
Pregnant women may be more susceptible to changes in temperature due to the extra physical and mental strain and may be at a greater risk, the researchers said.
In addition, women’s heat stress may result from increased fat deposition; the ratio of surface area to body mass, which reduces their ability to lose heat by sweating; weight gain that increases heat production; and the fetus adding to the maternal heat stress by adding its own body’s composition and its own metabolic rate.
The team developed a novel, high-resolution air-temperature estimation model to predict daily air temperature and estimated exposure to air temperature during various prenatal exposure periods from date of conception through birth for each mother.
The study showed that warm air temperature was associated with decreased birth weights.
“For example,” Kloog said, “an increase of 8.5 °C in the last trimester of average exposure was associated with a decrease of 7 grams in birth weight. We also found that high air temperature during pregnancy can cause preterm birth. To conclude, we found that exposure to high air temperature during pregnancy increases the risk of lower birth weight and shorter gestational age.”