Study Finds Link Between Air Pollution And “Silent” Miscarriages

Exposure to air pollution during pregnancy may increase the risk of “silent” miscarriages, according to the findings of a new study.

Chinese researchers indicate that exposure to common pollutants like particulate matter and carbon monoxide may increase a woman’s risk of having a silent or missed miscarriage in the first trimester. The findings were published October 14, in the journal Nature Sustainability.

Prior studies have shown links between air pollution exposure and increased risk of heart and lung problems, as well as risk of emphysema from long-term exposure. However, researchers wanted to focus on the effects on pregnancy.

Researchers in this latest study focused on missed or “silent” miscarriages, which occur woman suffers a miscarriage in the first trimester, but the placenta and embryonic tissue remain intact with no bleeding or apparent signs the fetus is no longer viable. Parents often believe the pregnancy is progressing normally and find out weeks later about the miscarriage at their next doctor’s visit.

Researchers analyzed records of more than 255,000 pregnant women from 2009 to 2017. They compared their exposure to air pollutants at home and work, including sulfur dioxide, ozone, carbon monoxide, and particulate matter (PM 2.5). These are pollutants that come from industries, households, and vehicle emissions.

Levels of pollution were calculated based on historic data gathered by the network of air monitoring systems around the Chinese capital, which is known for its bad pollution and murky, gray skies.

About 7%, or more than 17,000 women, had silent miscarriages in the first trimester. All four pollutants increased a woman’s risk of silent miscarriage. They also found that the risk of miscarriage was linked to increases in pollution concentrations, meaning the risk increased as the pollution levels worsened.

Prior studies have shown links between air pollution exposure and risks to the fetus during pregnancy. A study earlier this year indicated air pollution can negatively affect fetal heart development. Another study concluded air pollution exposure during pregnancy increased the risk of miscarriage.

Research indicates many types of air pollution can cross the placenta during pregnancy and greatly affect the growing fetus. Particulate matter is widely implicated in an array of negative health effects and leads to the deaths of more than 30,000 Americans every year. Because it is so small, smaller than the size of a single strand of hair, it is easily inhaled, enters the blood stream and can cross over into the placenta.

Air pollution leads to the deaths of more than 7 million people each year. The findings of the new study add to the growing body of evidence indicating air pollution has negative effects on the health of pregnant women and the growing fetus.

While the new study doesn’t prove cause and effect, the researchers say it shows an association between air pollution and miscarriages. More research is needed to determine the exact link, if any.