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2 May 2017

Study Reveals Link between Unusual Temperatures and Low Birth Weight


When it comes to unusual weather events, many point the finger at climate change and global warming being responsible. Rain in July or heat-waves in October can bring confusion and abnormality compared to the expected seasonal weather.

A new study across 19 US hospitals has linked unusual temperatures to effects on pregnant women and how their new-born’s weight may be affected by temperature anomalies. The study analysed over 220,000 babies who were born between 2002 and 2008, to see the link between temperature, location and birth weight.

Unusually cold temperatures were defined as those colder than the 5th percentile of average temperature for the location, and unusually warm temperatures were those above the 95th percentile of average temperature. During a women’s second trimester in Los Angeles for example, unusually cold temperatures were those below 56°F (13°C), while in Massachusetts, temperatures below 27°F (-2°C) were considered colder than expected.

Average temperatures for participating mothers were recorded for the entirety of the pregnancy, as well as during individual trimesters, and factors such as the baby’s sex and mother’s body mass index were taken into account during the study.

The results, taking all factors into consideration, revealed a link between exposure to unusual temperatures and low birth rate. Overall, women exposed to unusual temperatures throughout their entire pregnancy were about 2.5 times more likely to give birth to a lighter baby.

More specifically, women exposed to unusually cold temperatures during the second and third trimester, or unusually hot conditions in the third trimester, were more likely to have low-birth-weight babies by 18 to 31 per cent.

Senior author of the study Pauline Mendola – an epidemiologist at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) comments on the results: “Until we can learn more, it makes sense to reduce the amount of time that pregnant women are exposed to extreme hot or cold weather. For example, pregnant women might try to avoid prolonged outdoor exposure to extreme heat or cold whenever possible.”

No reasoning as to the link between unusual conditions and birth weight has been confirmed, however the researchers note it could be due to the fact that extreme temperatures could affect foetal growth as blood flow to the uterus may be reduced.

This research is a follow on by the same group of researchers, who previously analysed whether extreme or unusual temperatures cause mothers to give birth prematurely.


Laura Sewell

An aspiring journalist, Laura is our content writer intern.  Pop-punk gig-goer and drag queen enthusiast, Laura is working her way into the industry with an English A -Level and love of writing about anything and everything in tow.