Researchers Link Urban Smog Exposure to Miscarriages

NEWARK, N.J. (CN) – Expecting mothers are at a much higher risk of miscarrying in the first 18 weeks of their pregnancy if exposed to common air pollution like smog and fine particles, according to new research from the National Institutes of Health.

Published in the journal Fertility and Sterility, the study links exposure to ozone and particulate-matter pollution with a 12 percent and 13 percent greater risk of miscarriage, respectively.

More research is needed into why air pollutants appear to trigger miscarriages, but the scientists speculated that it could be related to increased inflammation of the placenta and oxidative stress impairing fetal development.

The study followed 501 couples in Michigan and Texas who were trying to have a baby from 2005 to 2009. Of those couples, 97 of the 343 who conceived lost their babies in the first 18 weeks, defined as an early pregnancy loss.

Miscarriages are defined as losses occurring before the 20th week, while stillbirths occur after.

Even more troubling, the study suggested that chronic exposure to pollutants may be more detrimental than acute exposures during the early weeks of pregnancy.

Ozone is a highly reactive form of oxygen found in urban smog that is created when common pollutants like nitrogen oxide interact with sunlight.

The study notes that air pollution poses risks for the mother’s own health, as well as her baby’s, since septic miscarriages can be life-threatening.

NIH investigator Pauline Mendola led the study at the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

In an earlier study this year, Mendola found that ozone exposure led to a 40 percent increase in stillbirth risk and was particularly dangerous in the days prior to delivery. She extrapolated that about 8,000 stillbirth deaths in the United States could be blamed on ozone exposure.

The researchers noted that they did not take into account indoor exposure to air pollutants or other adverse pregnancy outcomes, such as gestational age or birth size.

Mendola has called for more studies of larger populations on the subject, saying on a podcast in September that “stillbirth and pregnancy complications really merit more attention.” The NIH has conducted other studies linking air pollution to miscarriage or fertility problems. A 2009 study found that women who lived near heavy traffic in California were statistically more likely to miscarry in the first 20 weeks of pregnancy.

In 2005 Brazilian researchers found lowered sperm counts in mice exposed to greater air pollution.

Experts say that miscarriage occurs in roughly 20 percent of all pregnancies in the United States. The Centers for Disease Control and Prevention estimate about 24,000 stillbirths occur every year in the United States.

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