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Around the world last year, more than 134 million babies were born.

During that same 12-month period when so many lives were just beginning, nearly 80 percent of the global population experienced at least 31 days of extreme heat that was made at least two times more likely due to human-caused climate change. The children being born now will come to know a world that’s not only getting hotter, but also one that’s increasingly at risk of extreme weather and disaster. 

Yet while we often talk about climate change with the future of these children in mind, rarely do we consider the impact of the crisis now on the women who are giving birth to these generations. 

At a moment when reproductive autonomy is under political attack in the US, climate change is making it even more dangerous to have a uterus. The full range of climate-related threats to reproductive health is vast.

So today, we’re launching a new package of stories, produced in collaboration with Grist and The 19th, that will help you understand a few of the profound effects that global warming has on people who can get pregnant. 

International climate change panels have already made clear that women are more vulnerable to climate change than men, with extreme heat, weather, and acute climate disasters aggravating existing gender-based vulnerabilities, like domestic violence, inadequate access to health care, and financial insecurity. 

But there is another layer of climate impacts that fall along gendered lines: Research shows that climate change takes a particularly profound physical toll on people who can bear children — from menstruation to conception to birth. 

And it’s only now, after years of neglecting to study the climate-related health conditions that affect people who can get pregnant, the scientific and medical communities are beginning to understand the scope of these threats. 

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Because a pregnant person’s immune system ratchets down during those crucial nine months so as not to reject the growing fetus, the parent-to-be is left more susceptible to any number of the health issues that climate change is already amplifying.

Take infectious diseases like malaria that are spreading because of the changing climate — pregnancy triples your risk of contracting it. Sea level rise can infuse drinking water with salt, which could lead to high blood pressure — a risk factor during pregnancy for premature birth and miscarriage. And for those who have access to fertility treatment, which involves highly time-sensitive procedures, increasingly massive and intense storms are making assisted conception even more unpredictable. 

And maybe the one that feels most immediately tangible to anyone already sweating through this summer: Exposure to extreme heat during pregnancy increases the likelihood of preterm birth. 

Babies who are born prematurely, or prior to 37 weeks of gestation, can face a wide variety of health complications throughout their lives, including anemia, respiratory distress, jaundice, sepsis, and retinopathy — and, at worst, infant mortality.

Last week, a new study was published that provided the most compelling picture yet of the link between heat exposure and the rising rate of premature births. The nationwide study analyzed more than 50 percent of US births between 1993 and 2017. 

The study authors explained that they observed an increase in the rates of preterm and early-term births after spates of locally extreme high temperatures — providing stark evidence of increased preterm and early-term birth rates in response to heat waves.

The research is the largest study to date on the question of whether climate change and the more extreme temperatures it brings is impacting pregnancy. Finally — in the US and beyond — we have an answer: yes.

As similar studies around the world have found, there are stronger associations with preterm birth among certain population subgroups — with Black mothers around the world experiencing 2.5 times higher rates of heat exposure and negative birth outcomes than white populations.

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This troubling inequity is one that the research of Rupa Basu, an environmental health hazard scientist in California, would confirm in the years after she became pregnant with her second child in 2007. 

As Vox contributor Virginia Gewen wrote in her story, published today as part of our full package on climate change and reproductive health, Basu was troubled by her own body’s physical response to rising temperatures during the summer of her final trimester and wondered if there could be a biological mechanism at work.

As a scientist in the field of maternal health, she was shocked to find how little research had been done to explain the connection between heat stress and pregnancy complications. 

"If this is a biological response, imagine what’s happening in places like India and Africa where the heat can get to an unbearable 130 degrees Fahrenheit,” Basu remembers thinking. Basu knew that other vulnerable populations, notably the elderly, were particularly susceptible to heat. 

But she couldn’t find any answers to one fundamental question: Do higher temperatures lead to premature births or other pregnancy complications? 

As Basu prepared for her second baby’s delivery, she began gathering state weather data and birth records to identify preterm births, those that occur prior to 37 weeks of gestation. Basu analyzed 60,000 summertime births — those taking place between May and September — from 1999 to 2006, across 16 California counties.

She found higher rates of preterm births during higher temperatures. She published the research in 2010, and even though she focused on California, it was the first large-scale epidemiological study looking at preterm delivery and temperature conducted anywhere in the world. 

“How did we miss this for so long?” Basu asked. “Women are often the last to get studied. But the most vulnerable people are those who are pregnant.” 

You can read the rest of Basu’s story here and explore the rest of the project here. Vulnerabilities to heat exposure are only intensifying: In the last year, the hottest on record, 6.3 billion people experienced at least 31 days of extreme heat, hotter than 90 percent of documented temperatures between 1991-2020, according to a new report. 

These women’s stories are a warning to us all. 

—Paige Vega, climate editor

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And why the government wants you to drink it.

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