Women are more likely to have premature babies and high-risk pregnancies the more they are exposed to unconventional natural gas development, according to a new study based on more than 10,000 babies born in the shale-gas region of Pennsylvania.
The study, released by Johns Hopkins University Bloomberg School of Public Health on Thursday, found that mothers who lived near the highest levels of gas-industry activity were 40 percent more likely to give birth before 37 weeks of pregnancy than those where the industry was least active.
It concluded that women in the most active sections of the area studied were 30 percent more likely to have pregnancies labeled as high-risk because of factors such as high blood pressure or excessive weight gain.
And it found that, of the 10,946 babies born in the study area between January 2009 and January 2013, 11 percent were born before 37 weeks, classifying them as premature.
The study, based on data from the Geisinger Health System which covers 40 counties in heavily drilled northern and central Pennsylvania, measured gas-industry activity by including the distance to the mother’s home; the dates and durations of well-pad development, drilling and fracking, and the production volume during pregnancy.
It calculated the activity levels into four quartiles, and concluded that the highest-activity quartile was associated with the highest rates of premature births and high-risk pregnancies.
“There was an association between unconventional natural gas development activity and preterm birth that increased across quartiles,” according to the 10-page paper published in the journal Epidemiology last week.
It didn’t reach any conclusions about why increased exposure was associated with the pregnancy-related problems but said that every step of the gas-development process has an environmental impact that may harm air quality or add stress to the lives of expectant mothers.
“Now that we know this is happening, we’d like to figure out why,” said Dr. Brian Schwartz, a professor in the Department of Environmental Health Sciences in the Bloomberg School, who led the study. “Is it air quality? Is it the stress? They’re the two leading candidates in our minds at this point.”
He urged policymakers to take the conclusions of the study – titled “Unconventional Natural Gas Development and Birth Outcomes in Pennsylvania, USA” – into account in deciding how to regulate the industry.
“The first few studies have all shown health impacts,” he said. “Policymakers need to consider findings like these in thinking about how they allow this industry to go forward.”
Neil Shader, a spokesman for the Pennsylvania Department of Environmental Protection, said officials are reviewing the study and would have no immediate comment.
Schwartz said the study is the first to find a link between gas development, premature births, and high-risk pregnancies, but noted that it follows three related studies by other researchers.
One of the other studies, by University of Rochester researcher Elaine Hill, concluded in 2014 that unconventional gas development in Pennsylvania increased low birth weight of babies born to mothers living with 2.5 km of a gas well. Hill also studied babies in Colorado, concluding in 2013 that proximity to wells increased the incidence of low birth weight.
Hill said the Hopkins study has taken a “comprehensive” approach that has used some new data to make its case.
“The authors use electronic health records with exact addresses and are able to confirm that the mothers in their sample lived at the address throughout the length of the study,” Hill wrote in an email.
She noted that the Hopkins researchers cite previously unused data such as that from compressor stations to provide evidence for exposure to the effects of gas drilling, and use specific time points for the drilling process “which enhances the comprehensive nature of their methodology.”
Asked for her own opinions on the reasons for an association between gas drilling and premature births, Hill said the air pollution and stress on expectant mothers from nearby gas development are “plausible explanations.”
“Premature birth has been associated with the many air pollutants found in recent studies,” Hill told StateImpact. “Premature birth is also associated with maternal stress or risky pregnancies. These are plausible explanations for the findings in this study.”
Another study, by Lisa McKenzie of the University of Colorado at Denver, studied more than 124,000 babies born in rural Colorado between 1996 and 2009 and concluded there was an association between the density and proximity of gas wells and congenital heart defects among the infants.
Researchers at the University of Pittsburgh determined in June this year that there was a “small but significant” association between low birth weight and the mother’s proximity to unconventional gas drilling in southwest Pennsylvania.
One of the Pittsburgh study’s authors, Shaina Stacy, said the Hopkins study, though differing in some of its methods, broadly confirms the conclusions of the Pittsburgh research.
“Despite the differences in study design, the message is the same,” she said. “Living in areas under conventional natural gas development seems to increase the likelihood of adverse birth outcomes, lower birth weight, SGA [small for gestational age] and preterm birth,” Stacy wrote in an email.
Another author of the Pittsburgh study, Evelyn Talbott, said: “I see the overall results as very compelling and similar to ours.”
Talbott, a professor of epidemiology at the University of Pittsburgh, said the two studies differed in their inclusion of some elements such as education in the case of the Pittsburgh project, and duration of well pad development in the case of the Hopkins study, but reached similar conclusions.
In another project looking into fracking and health, a team from the University of Pennsylvania and Columbia University said this year that there was a link between rising hospitalization rates and natural gas activity in Pennsylvania’s shale gas region.
The latest study adds to concerns that fracking for natural gas may hurt human health, and highlights the need for more research, Schwartz said.
“More than 8,000 unconventional gas wells have been drilled in Pennsylvania alone and we’re allow this while knowing almost nothing about what it can do to our health,” he said.