(CNN) - A new study says pregnant women exposed to high levels of pollution might face an increased risk of having a "silent miscarriage" in the first trimester.
A silent miscarriage happens when a fetus hasn't formed or has died, but the placenta and embryonic tissue remain.
Researchers looked at data from more than 250,000 pregnant women in Beijing between 2009 and 2017.
They found women who lived in areas with higher levels of concentrated pollution saw a greater risk of miscarriage.
The authors of the study think "particulate matter" pollution is a problem because they believe particles can cross the maternal-fetal blood barrier and disrupt fetal growth and development.
The study was published in “Nature Sustainability.”