Extreme heat can increase the risk of preterm labor, which comes with potential lifelong consequences for the baby. Image Source: Stocksnap / Freestocks
Climate change is real — and millennials don't need tragic weather events like Hurricane Harvey or Irma to convince them. Nine out of 10 people under the age of 35 believe the climate is changing, according to a survey conducted in 2016. But while we might have our eyes open to scientific facts, we still have a lot to learn about how climate change will tangibly impact our everyday lives in the near future. Here's one way: a new study from George Washington University has found that climate change makes pregnancy even riskier, potentially leaving many women — and future generations of children — to bear the burdens of inaction on combating climate change.
Dangerous effects of extreme heat exposure include preterm labor, changes in birth weight, stillbirth, and neonatal stress.
Thanks to climate change, heatwaves are becoming more common. For their paper, Professors Leeann Kuehn and Sabrina McCormick conducted a review of existing academic literature to determine how these extreme weather events could negatively impact pregnancy outcomes. They closely evaluated 28 studies and found that dangerous effects of heat exposure include preterm labor, changes in birth weight, a rise in stillbirth rates, and neonatal stress. The study also notes that in the United States, extreme heat events are already causing more deaths than all other weather-related fatalities combined. The message is clear: if you are pregnant now or plan to be pregnant soon, this is an issue you should already be concerned about.
A 2017 Labor Day heatwave in San Francisco brought all-time highs of 106 degrees to the city and may have caused six deaths. Events like this are becoming more common. Image Source: Getty / Justin Sullivan
Why Pregnancy Makes You More Vulnerable During Heatwaves
Full disclosure: I happen to be eight months pregnant as I write this, and my pregnancy has spanned the entire Summer, which included some very hot days. At my first doctor visit, my provider gave me a helpful "welcome to pregnancy" booklet that included a long list of potential risks. It told me what beloved foods (unpasteurized cheese) and precious medications (Advil) to avoid and made recommendations about travel restrictions to places impacted by Zika. But it didn't mention anything about heat.
Pregnant women should be concerned if they stay in above-average temperatures for more than two days.
Based on this new study, doctors should tell pregnant women to take extra precautions during heatwaves when suggesting other lifestyle changes necessary for the health of the mothers and their fetuses. When I spoke with McCormick about her research, she explained that pregnant women cannot properly thermoregulate, which makes them especially vulnerable during heatwaves — and helps explain her conclusion that climate change will be worse for them than the general population. "Thermoregulation is the biological process of moderating one's own temperature in response to ambient temperature," McCormick explained. Pregnant women, older people, children, and infants have trouble with this thermoregulation process, which includes being able to know when you're too hot. "It is an issue that pregnant women might be exposed to the heat without knowing it's a problem until it's too late," she warned.
Generally, extreme heat can trigger a variety of dangerous health conditions in vulnerable populations, potentially putting expecting mothers at risk for things like heatstroke and respiratory problems. Dr. Iffath Hoskins, a clinical associate professor in the Department of Obstetrics and Gynecology at NYU Langone Health, elaborated on why she thinks it's important for pregnant women to take precautions: "High heat raises the mother's core temperature," she told me. This can cause dehydration, she said, which can pose risks to both the mother and the developing fetus. While the American Congress of Obstetricians and Gynecologists currently does not have specific guidelines for pregnant women and heatwaves, Hoskins said it's important for women to drink water (not soda!) and track their urine output, explaining, "If decreased, this means you are sweating out liquids and electrolytes, which are necessary for good fetal development."
Extreme heatwaves are more likely thanks to climate change, bringing more risks to pregnant women. Image Source: Getty / Chris Hondros
After learning all this, the first thing I wanted to know was: how hot is too hot? "It's a complicated question," McCormick admitted, noting her research suggests that the exact temperature varies based on where you live. "If you live in Florida and you're used to 90 degrees, then 90 degrees is not necessarily a big deal for you. But 100 degrees might be a big deal. If you live in Maine, then 90 degrees might be a really big deal for you." Based on the research she reviewed, McCormick says, pregnant women should be concerned if they stay in above-average temperatures for more than two days. In addition, she believes that one extreme exposure is probably worse than a lower-level, longer-duration exposure.
What's Really at Risk For the Fetus?
The entire list of pregnancy complications caused by exposure to extreme heat should cause concern — but McCormick says the risk of preterm delivery is the one most strongly backed up by the research. "That may be the most urgent. If you're very preterm it can have lifelong effects on a person, so we need to make sure we're keeping the number of preterm deliveries down as much as possible."
Preterm delivery is defined as any birth before 37 weeks. If a baby is born too early, there is a higher risk of infant death, and if the baby survives, early birth can lead to various immediate and long-term health problems. Those include respiratory, vision, and hearing problems, as well as social, emotional, and physical growth problems down the line. These challenges come with an economic burden, too. According to one study, the annual societal cost of preterm birth in the United States totals at least $26.2 billion. If climate change makes preterm labor increasingly likely, more families (and society as a whole) will have to face the economic and emotional challenges of caring for preterm infants as newborns and into adulthood.
It's not just preterm labor that pregnant women need to worry about as a result of climate-change-related heatwaves. Other concerns supported by the study include low birth weight, stillbirth, or heat-related distress after a baby is born. Dr. Hoskins notes that a rise in a woman's core body temperature can also be detrimental to the central nervous system (CNS) of the developing fetus, especially during the first trimester when the bulk of the CNS structures are being formed. "There is an association between high maternal core temperature and neural tube defects (spina bifida)," she explained. Considering these serious outcomes, pregnant women like me might find it surprising that heat exposure is not routinely raised as a potential concern during pregnancy. McCormick hopes her research will make that part of the conversation between healthcare professionals and expecting women, especially as extreme events become more likely. "It's my impression that pregnant women are not thinking about exposure to heat as a risk," she said. "It's something I'd like to put on their radar."
How the USA'S Lower Standard of Care Makes Things Worse
When it comes to extreme weather, it's always better to be prepared for the worst. "Care is super important in the context of any of the climate-change-related risks," McCormick explained. The better care you have, the more likely you'll be able to respond well to the effects. In the case of pregnancy, a woman could be exposed to extreme heat and go into preterm labor, but if she's caught in time with the right medical interventions, an early birth can be prevented or the most dire consequences avoided.
As climate change makes pregnancy more risky, it could place the long-term burdens on those who can't access quality care while pregnant.
Unfortunately, many pregnant women in America lack access to the quality prenatal health care that would help them mitigate the negative impact of extreme heat exposure. Recent in-depth reporting from NPR and Propublica revealed just how behind the US is compared to other developed countries when it comes to maternal health care. Among other troubling statistics, America has the highest rate of maternal mortality in the developed world — that means a woman is more likely to die from a pregnancy-related complication in the US than in any other developed country.
There is also clear evidence that the level of care differs based on race or economic status, too. Just look at America's infant mortality rate, which varies greatly depending on your race. In 2016, the mortality rate for black infants was more than double that for white babies. McCormick's research uncovered at least one example of how inequality may determine how climate change impacts pregnancy: a study that found that black infants are more likely to die during warm-season months in California than any other racial subgroup. It's a sad reality that unlike in other developed countries, every American citizen is not guaranteed the same basic level of quality and affordable health care. As climate change makes pregnancy more risky, it could magnify the consequences of our country's racial and economic inequalities, placing the long-term burdens of preterm birth and other complications on those who can't access quality care while pregnant.
What Can Be Done to Reduce the Risk to Pregnant Women?
McCormick says her paper is just the start and that more research must be done to determine how extreme heat impacts pregnancy. The first question she'd like to see explored further: when in pregnancy are women most vulnerable? "Based on the research we've seen so far, it seems like different kinds of adverse outcomes are affected at different times in the pregnancy," she said. For example, the risk of stillbirth may go up if you are exposed to extreme heat in your third trimester, whereas preterm delivery is a concern if you have an exposure in your second trimester. Women and their doctors need more information to prepare and react to the consequences of climate change.
A second question that needs to be explored: how much time does a pregnant women have to spend in the heat to pose a problem, especially when she has access to air conditioning? "The studies to date don't do a very good job of monitoring exactly what an exposure is," McCormick said. "It may be that if you spend the night in AC you're fine, even if you spent the whole day outside." Or, if it's 110 degrees and you're only out in it for two hours, are you still fine? "We don't have a fine-grain analysis that tells us when you're really safe and how much you really need to be exposed to have a problem," McCormick admitted.
Despite outstanding questions, the study's authors do believe there is enough startling information to take action based on what we already know. "First and foremost, we need to think about mitigating climate change as quickly as possible," McCormick told me. (Yet another reason pulling out of the Paris Climate Agreement was a step in the wrong direction.) "Secondly," she said, "we need to reconceptualize how we prepare for extreme heat events." Europe has moved faster in this area than the US, sadly because it's already seen mass-casualty events caused by heat. The 2003 heatwave in Western Europe caused up to 70,000 deaths. McCormick says smarter urban planning is one way to address potentially deadly heatwaves like these. "Often we think about access to air conditioning as the number one intervention on heat," she noted. "But in fact, AC itself creates hotter microclimates in places it's being used in addition to emitting greenhouse gasses." Air conditioning might work on an individual level, but it will likely compound the problem in the long run and doesn't do anything for those who don't have it. McCormick hopes her study prompts leaders to take a big-picture approach to helping future pregnant women avoid the consequences of climate change: "If we can use the expansion of green space and change transportation patterns to reduce the urban heat island effect, then we're addressing heat and heat exposure much more sustainably."
"Climate change is happening now, and it can span generations in a way we've haven't thought about."
Today, "once-in-a-lifetime" heatwaves, wildfires, hurricanes, and floods fill our social media newsfeeds on a regular basis. It's hitting closer and closer to home. This new study demonstrates clearly that climate change will impact the most intimate parts of our lives. It connects the abstract idea of "global warming" to an experience that is extremely personal and permanent: bringing a child into the world. McCormick hopes that highlighting this connection will help us comprehend how today's weather can have consequences that reach far into the future. These aren't problems we can solve by donating to victims of the latest climate disaster or by electing officials who opt for reactive disaster relief funding instead of proactive, long-term solutions. McCormick says her study proves that climate change will have "transgenerational" effects since one exposure could lead to lifelong effects in a woman's offspring. She added this warning: "climate change is happening now, and its impact can span generations in a way we've haven't thought about."