Typically, higher income levels are linked to healthier pregnancies and healthier babies. But does money truly play a vital role? Surprisingly, sedimentary rocks formed 390 million years ago may hold clues, particularly for residents above the Marcellus Shale formation, as discovered by a research team from Penn State.
The researchers studied the economic surge stemming from natural gas extraction in the Marcellus Shale, which injected billions of dollars into Pennsylvania from 2007 to 2012. They assessed various factors, including local incomes and birth weights, in school districts located above this extensive black rock formation that spans a significant part of Pennsylvania. In areas with high natural gas production potential, researchers noted that rising incomes across different socioeconomic backgrounds led to fewer instances of low birth weight, specifically those less than five and a half pounds.
More specifically, in a sample of 12,930 sibling pairs—one born before the economic boom between 2005 and 2007, and another born after between 2012 and 2013—the study revealed that the rate of low birth weight decreased by 1.5%, dropping from 6.3% to 5.8%. This increase in birth weight accounts for nearly 600 babies born at healthier weights, an essential factor for improved health outcomes, according to the researchers. Their findings were published in Demography.
“Infants born with low birth weight face higher risks of various cognitive and health issues, which can lead to lower educational success, lifetime earnings, and adult health problems,” said lead author Molly Martin, a Penn State professor of sociology and demography. “What we previously did not know was whether increases in income would enhance pregnancy and infant health outcomes.”
Birth weight is associated with numerous health outcomes for newborns, affecting immediate aspects such as breathing ability, immune system strength, and infant mortality, as well as long-term growth and disease susceptibility. To analyze how income increases in communities affect birth weight, pre-term delivery rates, maternal health, and behaviors prior to and during pregnancy—like smoking habits and adherence to prenatal care—the researchers employed a “quasi-experimental” design. This common method in social sciences assists in estimating causal relationships rather than simply noting correlations among variables.
“It’s impossible to assign people randomly to lives with differing resources,” Martin explained. She noted that the shale formation served as a distinct reference point, devoid of any social or cultural influences. “All the factors contributing to or resulting from an economic boom, such as development, job creation, or pollution, affect surface outcomes. The sections of the shale with the highest potential value predicted economic enhancements in the communities above.”
Martin described the Marcellus Shale economic boom as a “natural experiment” observing changing factors. The team utilized 21 datasets containing data on demographics, taxation, births, infrastructure development for drilling access, environmental impacts like pollution, and more from both national and state sources to control for any potential confounding variables. By focusing on sibling pairs, representing 271 districts, the researchers could further tighten controls and discount factors like differing parenting styles and genetic predispositions. Through this comparison, the observed benefits of increased income could be attributed to the anticipated economic value provided by the shale formation.
“Our map emphasizes the potential economic impacts based on the quality of the Marcellus Shale, rather than focusing solely on drilling,” Martin clarified. “Communities situated over areas estimated to have higher natural gas reserves enjoyed increased wealth—even when drilling was limited. Consequently, these areas experienced reduced rates of low birth weight.”
The rise in community-level income also corresponded to a 1.8 percentage point increase in the proportion of people receiving adequate prenatal care. Nonetheless, improvements in income did not enhance all pregnancy-related outcomes. Martin expressed surprise at the lack of progress regarding pregnancy health and health behaviors, such as gestational weight or smoking rates.
Alexander Chapman, a postdoctoral fellow at Penn State’s Edna Bennett Pierce Prevention Research Center, noted that the findings indicate community-level income growth contributes positively to the well-being of pregnant individuals and their newborns, even if individual behaviors remain unchanged.
“Income gains likely reduce stressors and hardships, or their effects, leading to better infant health,” Chapman stated.
Research is ongoing to delve deeper into how income increases influence families and children to shape public policies aimed at enhancing community health. According to Martin, their research underscores the significant advantages of broader economic improvements within communities.
“These findings reinforce other research emphasizing the importance of elevating living standards for health,” Martin remarked. “The development of the Marcellus Shale formation injected millions of dollars into various parts of Pennsylvania, far exceeding typical targeted funding increases for public assistance or infant health, benefiting individuals across all income levels.”
This project also involved contributions from Tiffany L. Green, an associate professor of obstetrics and gynecology and population health sciences at the University of Wisconsin-Madison.
The study received support from several organizations, including the Russell Sage Foundation, National Institutes of Health, National Institute on Drug Abuse, Society of Family Planning Research Fund, County Health Rankings and Roadmaps Program, Penn State’s Social Science Research Institute, Population Research Institute, Edna Bennett Pierce Prevention Research Center, and the University of Wisconsin’s Center for Demography and Ecology and School of Medicine and Public Health Centennial Scholars Program.
