Does traffic pollution cause early pregnancy loss?

Green S, B Malig, GC Windham, L Fenster, B Ostro and SH Swan. 2009. Residential exposure to traffic and spontaneous abortion. Environmental Health Perspectives doi:10.1289/ehp.0900943.

A study from California suggests that living closer to high traffic roads may increase the risk of spontaneous abortion in certain women. The association was seen only with African-Americans, not with women of other races.

Spontaneous abortion – or miscarriages before 20 weeks of gestation – occurs in approximately 10 to 15 percent of pregnancies. 

This is the first study to examine the association of living close to high traffic areas with spontaneous abortion.  However, exposure to environmental tobacco smoke –  which contains many of the same chemicals as automobile exhaust – has been shown to increase the risk of spontaneous abortion. 

Increased risk of spontaneous abortion was seen among African-American women living close to roads where traffic exceeded 15,000 vehicles per day.  Many large city streets have a daily traffic volume of 15,000 cars or more.  Overall, about 10 percent of women lived within 50 meters of a road carrying this traffic volume.  

In addition to African-American women, non-smokers were also at a 50 percent increased odds of spontaneous abortion if they lived near high traffic density roads. Surprisingly, living near busy roads appeared to decrease the risk of spontaneous abortion among smokers.

The researchers enrolled 5,144 pregnant women living in three regions of California early in their pregnancies. Their address at the time their pregnancy began was compared with California Department of Transportation data to determine the average annual traffic density in the area immediately around each woman’s home.  Because living in high traffic areas may also be associated with social factors such as income, education, age, or employment status, the analyses took these factors into account.