And new research suggests that the problem is only going to get worse.
Hot weather is more than just uncomfortable for pregnant women; it is potentially dangerous, sending them into labor earlier than anticipated. New research published in the journal Nature Climate Change reveals that, as global warming progresses, it increases risk of premature childbirth, which is linked to worse health and developmental outcomes in those children. Premature babies often struggle with respiratory and blood pressure issues, psychiatric conditions, and lower academic results.
Lead study author Allan Barreca, from the University of California, Los Angeles, went back to U.S. birth records between 1969 and 1988 and found that "an average of 25,000 children were born up to two weeks early during warmer than average periods." This equals 150,000 lost gestational days annually. From Phys.org's writeup:
"They found that early birth rates increased by five percent on days where the temperature was above 90 degrees Farenheit (32.2 Celsius), accounting for around one out of every 200 births."
This does not bode well for future children being born in a world where temperatures are currently 1 degree Celsius above pre-industrial averages and set to increase significantly. Barreca said, "We predict more than 1 in 100 births will occur earlier than expected in the U.S. by the end of the century. That number may seem small, but that's much higher than the risks of getting into a car accident." That adds up to 42,000 babies being born prematurely in the United States annually.
While the reasons for women going into early labor in hot weather are not fully understood, Barreca suggests it could be linked to increased levels of oxytocin, the hormone that regulates labor and delivery, or cardiovascular stress brought on by hotter weather, which can also induce labor.
Air conditioning is known to decrease the risk, but this can be inaccessible or expensive for some families. The Guardian cites Barreca saying that "electrification and access to air conditioning should be a part of any effort to protect pregnant women and infants in developing countries."