Women who live near fracking sites are more likely give birth prematurely and have high-risk pregnancies, according to researchers at Johns Hopkins Bloomberg School of Public Health.
The study, led by professor Brian Schwartz, was conducted in Pennsylvania and used data from Geisinger Health System, which covers 40 counties in north and central Pennsylvania, to reach the findings.
The researchers analysed the records of 9,384 mothers who gave birth to 10,946 babies between January 2009 and January 2013.
This data was compared with information about wells drilled for fracking and how close they were to the homes of the pregnant mothers, as well as what stage of drilling the wells were in, how deep the wells were dug and how much gas was being produced at the wells during the mothers' pregnancies.
Using this information, they developed an index of how active each of the wells were and how close they were to the women.
The researchers found that women living in areas of active drilling and production activity were on average 40 per cent more likely to give birth before 37 weeks of gestation (considered pre-term).
They also found a 30 per cent increase in the chance that an obstetrician had labelled their pregnancy "high-risk," a designation that can include factors such as elevated blood pressure or excessive weight gain during pregnancy.
When looking at all of the pregnancies in the study, 11 per cent of babies were born preterm, with the majority (79 per cent) born between 32 and 36 weeks.
"The growth in the fracking industry has gotten way out ahead of our ability to assess what the environmental and, just as importantly, public health impacts are," Schwartz said.
"More than 8,000 unconventional gas wells have been drilled in Pennsylvania alone and we're allowing this while knowing almost nothing about what it can do to health.
“Our research adds evidence to the very few studies that have been done in showing adverse health outcomes associated with the fracking industry."
Fracking in Pennsylvania has exploded in recent years. In 2006, there were fewer than 100 unconventional gas wells, now there are more than 8,000.
In the past, health officials have been concerned about the effect that fracking has on air and water quality, as well as the stress of living near a well where just developing the site of the well can require 1,000 truck trips on once-quiet roads.
A report published in October 2013 by the UK Department of Health sub-body Public Health England concluded that the risk to people's health from fracking was low, as long as the process is "properly run and regulated”.