Higher Temperatures Linked to Poorer Birth Outcomes

THURSDAY, Nov. 5, 2020 — Higher temperatures are associated with increased odds of preterm birth, reduced birth weight, and stillbirth, according to a review published online Nov. 4 in The BMJ.

Matthew Francis Chersich, from the University of Witwatersrand in Johannesburg, South Africa, and colleagues conducted a systematic review and random effects meta-analysis of clinical studies to examine whether exposure to high temperatures in pregnancy is associated with an increased risk for preterm birth, low birth weight, and stillbirth. Data were included from 70 studies, set in 27 countries.

The researchers found that preterm births were more common at higher than lower temperatures in 40 of 47 studies. The odds of a preterm birth increased 1.05-fold per 1-degree Celsius increase in temperature and 1.16-fold during heatwaves in the random effects meta-analysis. In 18 of 28 studies, higher temperature was associated with reduced birth weight, with considerable statistical heterogeneity. There were associations observed between temperature and stillbirth in all eight studies on stillbirths, with a 1.05-fold increase in stillbirths per 1-degree Celsius increase in temperature. Women in lower socioeconomic groups and at age extremes had the largest associations between temperature and outcomes.

“Given increases in the frequency and intensity of heatwaves, the number of pregnant women exposed to these conditions worldwide, and the significant individual and societal burdens associated with preterm birth and stillbirth, research and policy initiatives to deal with these connections are a high priority,” the authors write.

Several authors disclosed financial ties to companies that have interests or investments in coal mining, renewable energy, and fossil fuels.

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