Pregnant Women Have a Higher Risk of Delivering Early on Unseasonably Hot Days
By Alan Barreca
About a quarter of children in the U.S. are born two to three weeks before their due date, which qualifies them as "early term." Pregnancies typically last 40 weeks, so you might think that being born two to three weeks early wouldn't matter.
But, children born just two or three weeks early are at slightly higher risks of respiratory problems, like asthma, later in childhood. About 1 in 10 children in the U.S. are born more than three weeks before their due date, which qualifies them as "preterm" and puts them at higher risks for much worse outcomes.
Hot weather is one potential risk factor in early deliveries because heat exposure can increase the mother's level of oxytocin, a hormone that regulates delivery. Despite the plausible link, questions remain about the number of deliveries affected by hot weather every year in the U.S. or if hot weather accelerates the timing of delivery by hours, days or weeks.
I'm an economist who has spent much of my decade-long career investigating how weather affects human health, with a focus on child and maternal health. I got started down this career path in 2008 because I wanted to understand why infant health is much worse today in hotter parts of the U.S., like Louisiana. Now, I work on these issues to help identify unknown health-related threats from climate change.
New Evidence on Temperature and Delivery Risk
My latest work with Jessamyn Schaller at Claremont McKenna, published in the Dec. 2, 2019 issue of Nature Climate Change, focuses on the effect of hot weather on early deliveries. We compiled 56 million birth records from the U.S. over the 1969-1988 time period. We then matched the recorded county of birth to daily weather data to see if hot weather does, in fact, lead to earlier deliveries.
But, there were two data challenges we needed to overcome.
First, hotter places have other problems, many of which aren't related to the climate. More people in Mississippi, for example, do not have health insurance.
To get around this challenge, we analyzed time periods with unpredictably hot weather, which we define as an excess of days with maximum temperatures of 90 degrees Fahrenheit (32 degrees Celsius) or higher for a given county and time of year. This approach controls for slow-moving societal changes that affect infant health independent of the weather, like access to health care.
Second, measuring pregnancy duration (or what obstetricians call gestational length) is difficult. Pregnancies technically begin on the start of the last menstrual period prior to conception. Some mothers might recall this date, but the data suggest that there's a lot of guessing going on, either on the hospital's or the mother's side.
Here's where our study gets creative. We tested for shifts in the timing of deliveries. Take a hypothetical example: We might observe 10 more births than average in DeKalb County, Georgia, one of many counties in our data, on an unusually hot day for that time of year. Supposing the hot weather caused those births to occur two days early, we should observe 10 fewer births than average for DeKalb County two days later after the hot weather subsides. With this approach, we only need data on weather and birth dates, and not the start date of the pregnancy.
Our estimates imply that about 5% more children are born on unpredictably hot 90 degree-plus Fahrenheit days than would be expected. In total, hot weather caused about 25,000 babies each year to be born earlier than they would have otherwise in the U.S. The average loss is about six days of gestation. But, the losses were potentially as large as two weeks for some births.
Lessons for Climate Change
This isn't the first study to consider how weather might influence fetal health. A number of studies look at preterm delivery (less than 37 weeks gestation), although using very small samples. Our creative approach and large dataset enabled us to calculate weather-related reductions in gestational lengths across the entire U.S.
Unfortunately, we can't give the specific reason why hot weather causes earlier deliveries. It may or may not be because hot weather increases oxytocin and induces labor. And, it's not clear how much worse off these children will be as they grow into adulthood for being born a little early, especially since we can't tell whether the births qualify as preterm or early term. But, one recent study did find that fetal exposure to hot weather has lasting impacts into adulthood.
The risks for women delivering early are likely to increase in the coming years with climate change. Of course, the exact reductions in gestational length are difficult to predict because it's unclear what our future world is going to look like once 90 degree-plus F (32 degree-plus C) days become much more frequent.
But, to give you a sense of the magnitude, we predicted that more hot weather from climate change would induce about 42,000 additional deliveries annually in the U.S. by the end of century. That's more than 1 in every 100 births.
Air conditioning is likely to be an important solution, and is something we see in our data. But, without using greener air conditioners and renewable energy sources it will make climate change worse.
Given air conditioning is costly, climate change is likely to not only be a threat to child health, but would also put a financial strain on many households' tight budgets.
Alan Barreca is an associate professor of environmental economics at the University of California, Los Angeles.
Disclosure statement: Alan Barreca received funding to conduct this research from the California Strategic Growth Council.
Reposted with permission from The Conversation.
- 'Every Child Born Today Will Be Profoundly Affected by Climate ... ›
- Immediate Action Needed to Avoid Thousands of Heat-Related ... ›
- 5 Great Public Health Resources for Dealing With Extreme Heat ... ›
By Julia Conley
A federal judge in Washington, D.C. late Sunday struck down the Trump administration's proposed changes to the SNAP benefits program, potentially saving hundreds of thousands of people from losing badly needed federal food assistance.
<div id="e8d44" class="rm-shortcode" data-rm-shortcode-id="be49aabc36a5465eed30ca54f88f6b2d"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1318171686232096772" data-partner="rebelmouse"><div style="margin:1em 0">A judge has ruled in our favor and blocked the Trump administration’s unlawful changes to SNAP. This decision is… https://t.co/5zeTafxMLm</div> — NY AG James (@NY AG James)<a href="https://twitter.com/NewYorkStateAG/statuses/1318171686232096772">1603111595.0</a></blockquote></div>
<div id="f47ab" class="rm-shortcode" data-rm-shortcode-id="381daa45528adda7398d5628d047294f"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1318175677724676096" data-partner="rebelmouse"><div style="margin:1em 0">There's a lot of competition for Vilest Policy Ever, but slashing food stamps during a pandemic that's causing mass… https://t.co/EYvb0C8Q3m</div> — Tamar Haspel (@Tamar Haspel)<a href="https://twitter.com/TamarHaspel/statuses/1318175677724676096">1603112546.0</a></blockquote></div>
<div id="946d8" class="rm-shortcode" data-rm-shortcode-id="3cff2dc2643fc55ab21d2a73881c7de8"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1318168614541950976" data-partner="rebelmouse"><div style="margin:1em 0">Trump: yes to Space Force, no to Food Stamps. Another equation that might be remembered in a few weeks. https://t.co/9IEDBaMy2o</div> — Matt Taibbi (@Matt Taibbi)<a href="https://twitter.com/mtaibbi/statuses/1318168614541950976">1603110862.0</a></blockquote></div><p>"Trump: yes to Space Force, no to Food Stamps," Taibbi tweeted.</p>
- Trump Wants to Replace Food Stamps With Food Packages ... ›
- Trump Complains Puerto Rico Getting 'Too Much' Disaster Aid as ... ›
- Trump USDA Resumes Effort to Cut Food Stamp Benefits - EcoWatch ›
EcoWatch Daily Newsletter
By Andrea Germanos
A group of Indigenous women and their allies on Monday urged the heads of major global financial institutions to stop propping up the tar sands industry and sever all ties with the sector's "climate-wrecking pipelines, as well as the massively destructive extraction projects that feed them."
- Global Banks, Led by JPMorgan Chase, Invested $1.9 Trillion in ... ›
- Keystone XL Pipeline Construction to Forge Ahead During ... ›
Poor eating habits, lack of exercise, genetics, and a bunch of other things are known to be behind excessive weight gain. But, did you know that how much sleep you get each night can also determine how much weight you gain or lose?
In January of 2019, a concerned citizen in Marion County, Florida noticed something strange: Someone was trapping flying squirrels.
The process of preparing and mixing a baby bottle formula seems innocuous, but new research finds this common occurrence is actually releasing millions of microplastic particles from the bottle's lining, Wired reported.
- Microplastics Found in Human Organs for First Time - EcoWatch ›
- Microplastics Are Raining Down on Cities - EcoWatch ›
- People Eat 50,000+ Microplastics Every Year, New Study Finds ... ›