Heat Waves Linked to Preterm and Early-Term Births, New Study Reveals

A new study has revealed a link between heat waves and early births.

The researchers of the study analyzed 53 million births throughout the 50 most densely populated metropolitan areas in the US. They did so from 1993 up until 2017 in a period of more than 25 years.

Heat Waves and Early Births

To date, this study is the largest, multi-institutional study into the link between high temperatures and pregnancy. The findings revealed that preterm and early-term birth rates slightly went up after the pregnant women went through increased temperatures for over four straight days.

Howard Chang, PhD, biostatistics and bioinformatics professor and a senior author of the study, said that the study reveals that the heightening temperature could imply worse outcomes for babies. This is due to how babies who are prematurely born may experience health issues. These could also incur further healthcare costs.

The researchers discovered that after experiencing at least four consecutive days of extreme heat, there is a 3% higher chance of having early-term births and a 2% higher chance of having preterm births.

Preterm birth refers to delivery at under 37 gestational weeks. It is the top infant mortality cause and could result in persistent health challenges.

On the other hand, early-term infants are those babies who are born between 27 to 38 gestational weeks. They also go through higher mortality compared to babies who are born at 39 to 40 gestational weeks.

The researchers explained that heat waves were positively linked to daily early-term and preterm birth rates. This reveals a dose-response link with heat wave temperature and durations and stronger links in the four-day window.

Among the analyzed births, 30% of the mothers were under 25 years of age, while 53.8% were aged 25 to 34, and 16.3% were over 35 years of age.

The researchers examined the data between October 2022 and March 2023 in the National Center for Health Statistics.

Findings were noted in the "Preterm and Early-Term Delivery After Heat Waves in 50 US Metropolitan Areas" study. The study was conducted by researchers from Emory University, Yale University, University of Nevada Reno, University of Utah, and the National Center for Atmospheric Research.

ALSO READ: Extreme Heat Waves: How High Temperatures Affect Physical, Mental Health

Climate Change Health Implications

Professor Chang explained in a press release that they are forecasting that summer this year would be extremely warm. Moreover, due to climate change, more heat waves could also occur.

Copernicus, the climate change service of Europe, announced in December 2023 that the world went through history's hottest year on record.

The summer of 2023 saw unparalleled triple-digit temperature stretches across the southern US and the entire world. In July, the planet saw its hottest day on record for four days in a day.

The National Weather service says that compared to other weather disasters in the US, heat kills more people on average.

In order to stay healthy and protected amidst scorching heat, it is important to hydrate, avoid overexerting oneself, and seek medical attention if a heat-related illness is suspected.