About 140 million babies were born globally last year—the equivalent of adding an entire new Russia to the world’s population. Not counted among those typically blessed events are the number of families whose pregnancies end tragically. According to the United Nations Interagency Group for Child Mortality Estimation, about 2 million pregnancies around the world end in stillbirth each year. The causes of natal death are numerous—from fetal abnormalities to labor complications to maternal hypertension to infections to placental malformation.

Now, according to a new study in Nature Communications, there is another, particularly pernicious cause that may account for up to 39.7% of stillbirths in low- and middle-income countries: air pollution, specifically in…