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Cherise Udell moved to Utah during the winter of 2005 while she was pregnant with her second child. A California native, she was familiar with horror stories about smog hovering over Los Angeles and the Golden State's overall reputation as a magnet for air pollution in some parts.

So she was floored when she arrived in Utah and experienced her first inversion, realizing that Utah's beautiful mountains were also home to a dirty secret at wintertime.

"I didn't realize how bad the air pollution was here. I had never heard of an inversion before," said Udell of Salt Lake City. "I instinctively knew that this was not healthy for my baby. I felt like I was walking around in a windowless room full of chain smokers."

The experience prompted Udell to form Utah Moms for Clean Air, a local group that has grown to nearly 3,500 members and advocates for cleaner air in the state. She also took a deeper personal interest in the subject, delving into science based-research that pointed to cases of lower birth rates, more cases of premature births and on increased asthma in children born in areas with bad air. As air quality continues to gain traction as an important public policy issue, Udell said she increasingly hears from mothers who are concerned about the effects of air pollution during their pregnancies.

That's the case as well for many practicing obstetricians and gynecologists across Utah, who field queries from worried mothers about what they should do if pregnant during poor air quality months. Some physicians have seen expectant mothers try to time pregnancies so their children aren't born during inversion periods.

But that's not possible for all mothers—and research is still ongoing about the exact effects of air pollution on pregnancy and infants, said Kirtly Parker Jones, M.D., a reproductive medicine specialist at University of Utah Health Care's Department of Obstetrics and Gynecology.

Still, it never hurts to take precautionary measures on bad air days, she advises.

"What to do if you're pregnant on bad air days? I'm not suggesting you get in your car and go to Park City," she said, but added small steps — like staying inside, purchasing an air filter for your home and not contributing to smog by maximizing trips — could make a difference.

The U.S. Environmental Protection Agency offers similar advice and has also researched the health effects of bad air on pregnant women and newborns. In a report titled "Promoting Good Prenatal Health: Air Pollution and Pregnancy," the EPA warns that prenatal exposure to pollutants increases risk of preterm delivery and low birth weight — factors that can compound to other problems for babies, including developmental disabilities later on.

The EPA findings may be supported by local research currently underway by Jeanette Chin, M.D., an assistant professor in the Maternal-Fetal Medicine division of the U.'s Department of Obstetrics and Gynecology. Earlier this winter, Chin received funding from the University of Utah's Program for Air Quality Health and Society to study health outcomes of children born at hospitals near the Geneva Steel Mill in Utah County in the 1980s. Hospitals saw fewer preterm births during a 13-month strike at the mill in Orem, which could be a result of less air pollution distributed during the strike period. Chin is studying health outcomes of children born during the strike and their siblings who were born at a time when the mill was emitting more pollution by using data collected through the Utah Population Database.

As research on air pollution and its effects on pregnancy and birth advances, groups like Utah Moms for Clean Air will continue to have conversations around the issues, said Udell. She bought an air filter after arriving in Utah and is careful to limit her children's activity outside during inversion months — measures other moms are routinely taking as well, she said.

Jones noted that family physicians, pediatricians and OB/GYNs are happy to discuss concerns about air quality with their patients and can provide more recommendations for how to weather the bad weather so families can live a healthier life.

Melinda Rogers is a communications specialist at University of Utah Health Care.