Air Pollution Is as Bad as Smoking When It Comes to Miscarriage Risk

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A new study has found that even short-term exposure to polluted air can have serious consequences for pregnant women.

Exposure to air pollution is as dangerous for pregnant women as smoking when it comes to raising the risk of miscarriage. A new study has found that, when women are exposed to elevated levels of air pollution for up to seven days, they experience a 16 percent increase in the likelihood of miscarriage.

The research was conducted by Dr. Matthew Fuller, an assistant professor of surgery at the University of Utah, and research analyst Claire Leiser. Fuller, who is not originally from Salt Lake City, where the study took place, said he noticed an anecdotal increase in miscarriages following periods of elevated air pollution and wanted to investigate further.

He and Leiser conducted a retrospective study of data on 1,300 women who had visited the emergency department at a single hospital in Salt Lake City between 2007 and 2015 and were carrying fetuses up to 20 weeks' gestation. After accounting for other physical factors and maternal age that could trigger a miscarriage, the researchers found that "the strongest link with a lost pregnancy was the level of NO2 in the seven days before the miscarriage."

NO2 is generated by burning fossil fuels, particularly diesel. Fuller and Leiser discovered that "the average seven-day NO2 level across the whole period was 34 micrograms per cubic metre (μg/m3), but peaked at 145μg/m3." When it peaked, it was associated with that 16 percent increase in miscarriage risk, which is similar to the risk posed by tobacco smoke in the first trimester.

Salt Lake City air pollution

© EurekAlert – Pollution in the Salt Lake City valley

This finding is profound and disturbing, especially since many cities are far more polluted than Salt Lake City, whose air quality levels are roughly on par with Paris and London (still bad, of course). As Fuller said,

"Many of us think there is an effect [of air pollution] on our health, but to find out there are actual effects on unborn children is very upsetting."

It's unclear exactly how polluted air leads to miscarriage, but it is thought that pollutants cause oxidative stress and inflammation.

What the researchers were unable to pinpoint is a precise gestational age at which fetuses are most vulnerable to air pollution, but this will hopefully be the topic of further research.

It's not the first time that air pollution has been linked to serious problems in pregnancy. Other studies have found it increases risk of birth defects, low birth weight, premature birth, and irregularly-shaped and smaller sperm that make it harder to get pregnant.

In the meantime, Fuller suggests that pregnant women avoid physical exertion on days with worse air quality or wear a particulate respirator face mask when heading out, and install indoor air filters at home, if possible. They could also time their pregnancies to avoid periods of elevated air pollution.