Global warming may increase number of early births

Scientists say birth rates rise during heatwaves but that air conditioning could provide the solution

HEATWAVES may increase the number of babies born early, scientists have warned, after finding a spike in early births when temperatures hit 90F (32.2C) or above. University of California

Los Angeles (UCLA) researchers, looked at the birth records of 56million Americans born from 1969 to 1988.

They found a rise in temperatures led women to give birth an average of 6.1 days earlier than the due date. Some went into labour two weeks early.

Birth rates increased by five per cent on days with a maximum temperature above 89F (31.6C).

Although the births were not early enough to count as premature – more than three weeks before the due date – experts fear it could still impact development. Shorter gestation periods have been linked to physical and mental health problems in adulthood, with a recent study suggesting it may even damage future earning potential.

Arizona State University found an extra day with mean temperatures above 89.6F (32C) in the womb is associated with a 0.1 per cent reduction in annual earnings at the age of 30.

The problem could get worse due toclimate change, the scientists warned.

Writing in the journal Nature Climate Change, Dr Alan Barreca, from

UCLA, said: “Exposure to extreme heat causes a large increase in delivery risk. While we posit climate change will cause gestational losses, the exact magnitude of the future costs is highly uncertain.

“Households may adapt as expectations about the frequency of hot weather events increase, which could mitigate impacts on infant health. Indeed, we find that access to air conditioning is an effective adaptation strategy.”

Dr Barreca said there was likely to be a greater impact on people in colder climates who were less likely to have air conditioning, but said the risk was global. “We ... found the risks were much more reduced once the population had air conditioning,” he added.

Prof Andrew Shennan, a consultant obstetrician from King’s College London, said: “Extremes of temperatures, both hot and cold, were previously linked to risk of both stillbirth and delivery. Mechanisms are not clear.”

Prof Shennan warned that some of the study’s results could be skewed by women choosing to deliver early if they become uncomfortable in the heat.

This summer, a weather station at the University of Cambridge recorded a temperature of 101.7F (38.7C), Britain’s highest ever, while the Met Office warned that the summer heatwave of 2018 would be normal by 2050.

The numbers of days where temperatues exceded 90F (32.2C) per decade were: four in the Sixties; 26 in the Seventies; 12 in the Eighties; 39 in the Nineties; 33 in the 2000s; and 35 in the 2010s.