A New Jersey based study from the Robert Wood Johnson Medical School compared estimated daily concentrations of various air pollutants with risk of stillbirth. The study covered delivery information from 1998 to 2004, and concerned only mothers who lived within 10 kilometers of New Jersey's 25 pollution monitoring stations. The abstract is available through the on-line version of the American Journal of Epidemiology, and the full text can be viewed with a subscription.
Using all the data, the researchers were able to find several trends. Some pollutants, like nitrogen dioxide, can be harmful during any part of pregnancy. In women who were exposed to a 10-parts per billion increase in nitrogen dioxide were 27 times more likely to have a stillbirth. Other pollutants appeared more harmful only at certain times in pregnancy, such as sulfur dioxide. Risk of stillbirth increased 13 percent for every 3-parts per billion increase of sulfur dioxide during the trimester, and 26 percent for every 3-parts per billion increase in the third trimester. Carbon monoxide appeared most dangerous during the second and third trimesters. At a 400-parts per billion increase in concentration, CO2 was associated with a 14 percent increased risk of stillbirth.
Due to limitations of the study, the research team could not say if less pollution would lead to a lower overall stillbirth rate. More study will be necessary to see how strong the link truly is, and analyze the effects in other populations as well. They were also unable to speculate about why exactly air pollution is dangerous to a fetus when it would seem most detrimental to a woman's lungs.
The study authors also reminded readers that the easiest way to eliminate exposure to these kinds of air pollutants is for women to avoid exposure to cigarette smoke.
The takeaway message for women is one of caution. It's not always easy to control your environment, particularly if you travel. Remember, this study isn't conclusive, so it's not realistic or practical to attempt avoiding all air pollutants. However, there are a few things you should know:
- If you smoke, quitting will reduce the risk of many complications for you and your baby.
- If you're around people who smoke, consider asking them to keep their smoking to a specific area that you can avoid.
- If you live in an area known to have high levels of air pollution, you should be alert to any signs of possible stillbirth. Do your fetal movement counts and don't hesitate to call your doctor if you have any concerns.
Photo © Adam Jackson