Hot weather linked to rise in early childbirth

Henrietta Strickland
December 5, 2019

The study doesn't explain the connection between extreme heat and earlier births.

According to Barreca, one simple measure could lower pregnant mothers' risk of heat-related early labor: air conditioning. Another study predicted that the annual number of days with temperatures above 100 degrees Fahrenheit (38 degrees Celsius) will double by 2065, compared to the end of the 20th century.That means far more babies are likely to come early."We predict more than 1 in 100 births will occur earlier than expected in the USA by the end of the century", Barreca said.The study authors offer two possible reasons why extreme heat causes an increase in early births: Either pregnant mothers get dehydrated, which causes increase in their levels of oxytocin (a hormone that regulates the onset of delivery), or the heat puts the mother under cardiovascular stress. Now, a new study has uncovered how climate change is having an insidious effect on pregnant humans. In a report released last summer by the Union of Concerned Scientists (UCS), scientists estimated that 160 urban areas in the United States will end up with at least 30 days each year that exceed a life-altering heat index of 105ºF. Births rates are also elevated on the following day, perhaps because labor and delivery continued into the next day, the study said. This large study encompassed 56 million births. The researchers used a spike in birth rate on days hotter than 90 degrees as a proxy for early births, rather than counting the length of pregnancy recorded on birth certificates.

"We realized that the way people had worked at studying the health impacts of extreme heat in third trimester needed a new look", Barreca told Salon. In their report, investigators Barreca and Schaller analysed U.S. government data on weather and birth rates for the years 1969 to 1988. Barreca says this corroborated the idea that births occurred earlier than expected.

Looking at 20 years of data on heat waves and birth timing across the United States, researchers "estimate that an average of 25 000 infants per year were born earlier as a result of heat exposure".

"But developed countries, like the United States or England, should pay developing countries for them to electrify with the help of renewable sources, such as wind or solar power., in order to avoid producing more greenhouse gas emissions".

Factoring in current climate model predictions about extreme heat, humans may lose 250,000 additional days of gestation per year by the end of the century overall. Another reason could be cardiovascular stress.

The research adds to existing knowledge on health complications tied to extreme temperatures.

Of course, the impact of rising global temperatures on infant health may depend on a pregnant woman's income - and her access to air conditioning, the researchers said.

"Our study suggests is that air conditioning is an important mitigator and adaptive strategy, but air conditioning is expensive and those who are quickest to have it on and run their air conditioner all day in that comfortable range are people who are well off economically", Barreca said. Add Climate Change as an interest to stay up to date on the latest Climate Change news, video, and analysis from ABC News.

Air conditioners could helpWhen greenhouse gases from the burning of fossil fuels enter the atmosphere, they trap more heat on the planet, causing Earth's surface temperatures to rise.

Other reports by Click Lancashire

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