Early childbirth linked with hot weather, according to US study

on 04 February 2020

A study in California has linked hot weather to a spike in babies being born early in the US between 1969 and 1988.

Researchers said that an average of 25,000 babies were born up to two weeks early during warmer weather – equivalent to 150,000 lost gestational days annually.

From the Institute of the Environment and Sustainability at the University of California-Los Angeles, Alan Barreca, one of the researchers of the study, said: “Hot weather increases maternal levels of oxytocin, which is a key hormone that regulates labour and delivery. But the link could be because hot weather causes cardiovascular stress, which might lead to early deliveries.”

As part of the study, which was published in Nature Climate Change, researchers used daily estimate shifts in daily birth rates from US states over a 20-year span, which created a sample of around 56 million births.

The data showed that early birth rates spiked by 5% on days where the temperature was above 90 degrees Fahrenheit.

With temperatures currently around 1C hotter than pre-industrial averages, researchers predict climate change will impact weather-linked early birth rates in future.

“We predict more than 1 in 100 births will occur earlier than expected in the US by the end of the century.

“The number may seem small, but that’s much bigger than the risks of getting into a car accident,” he added.

However, commenting on the study Professor of Obstetrics at King’s College London, Andrew Shennan, said that extreme temperatures have long been linked to the risk of premature childbirth, but the nature of the link was unclear.

“Given the wide variety of temperatures around the world, and that most women have normal pregnancies, this is unlikely to be an important risk factor for any individual,” he said.

The research ‘The Impact of high ambient temperatures on delivery timing and gestational lengths’ abstract can be found here.

Quote source: Phys.org