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Love is in the air this time of year. But for young couples looking to start a family, there is something else in the air that may hinder that pursuit.

Recent studies have linked exposure to urban air pollution with stillbirth, preterm birth, birth defects and low birthweight. City smog is also tied, physicians say, to pregnancy complications such as preeclampsia, premature membrane rupture and intrauterine growth restriction — a condition that occurs when the fetus does not receive adequate support from the mother via the placenta, resulting in extremely low birthweight.

Area doctors gathered with concerned citizens at the Salt Lake City Library on Thursday evening to discuss a growing body of research that suggests air pollution may have far-reaching impacts on human reproduction.

The presentation was the second of three educational seminars sponsored by Utah Physicians for a Healthy Environment; the third and final event will begin Tuesday at 7 p.m. in BYU's Joseph Fielding Smith Building.

Exposure to air pollution is risky regardless of the stage of pregnancy in which it occurs, the doctors said. In the first trimester, exposure is most likely to cause significant birth defects, miscarriage or stillbirth. By the second, they said, the greatest risk is neurological changes. Autism, for example, has been linked to exposure to air pollution.

But other developmental and behavioral changes may be caused by airborne pollutants as well, said Brian Moench, president of Utah Physicians for a Healthy Environment

Moench explained that during pregnancy, tiny particles of pollution are capable of passing through the placenta and entering the fetus. Because most pollutants are fat-loving chemicals, he said, these particles often build up in the brain, sometimes to the point of causing structural changes associated with developmental delays, autism and schizophrenia.

One study found an average loss of five verbal IQ points in children exposed to air pollution in the womb, Moench said.

These changes appear to affect male children more than females, he said.

In the third term, and even in the last seven days of pregnancy, the fetus supply of oxygen via the placenta is most at risk. Hannele Laine, an OB-GYN at the Avenues Women's Center, said exposure to air pollution appears to cause structural changes in the placenta that are associated with oxygen deprivation and complications like pre-eclampsia, low birthweight and premature birth.

And the effects of air pollution may begin even before conception.

Matthew Peterson, chairman of the Department of Obstetrics and Gynecology at University of Utah Health Care, spoke of personal experiences that led him to believe air pollution can degrade fertility — especially in men.

In the early 2000s, Peterson said, he helped the University of Utah relocate its in vitro fertilization lab to a different location. The new location was equipped with a more up-to-date air filtration system. Immediately after making the move, he said, the clinic noticed a 10 percent jump in the number of implantations that produced a "take-home baby."

Later, Peterson said, he helped set up a similar clinic in a polluted industrial city in Russia. Despite using the same equipment and technique, he said this clinic was only able to achieve a successful pregnancy about half as often as U.S. clinics. Upon further investigation, said Peterson, his team began to notice some abnormalities.

"As we looked at some of their cases, we saw sperm levels were very abnormal," Peterson said. "Also, women there had less eggs to begin with."

Since then, he said his Utah clinic has noticed a trend: two months after northern Utah has an inversion, men's sperm counts drop.

Those sperm are also less likely to be healthy, Laine said. After exposure to PM 2.5 — the tiny particulates that are the primary component of Utah's infamous inversion smog — sperm are less mobile and more likely to contain abnormal DNA. These kinds of defects, she said, can result in life-altering conditions like Down Syndrome.

Women's fertility is also affected, but less directly, Laine said. One study found female mice whose mothers were exposed to air pollution during pregnancy had 70 percent fewer eggs at puberty.

"One significant inversion like what we're having right now can have an impact on the health of three generations, maybe more," Moench concluded.

Twitter: @EmaPen ­—

What to do when air is bad

How to limit your exposure to air pollution:

Do not exercise outdoors during periods of poor air quality.

When exercising, avoid busy roads.

Do not burn wood, coal or charcoal indoors or outdoors.

Use a furnace filter in your home with a MERV rating greater than 10.

Use the recirculate setting on your air conditioner in your car.

If you wear a respirator or mask, look for a rating of 95 to 99.