Air pollution raises preterm birth risk

Exposure to air pollution later in pregnancy raises a woman's risk of delivering prematurely.

Some previous studies have linked air pollution exposure in both the first and third trimester of pregnancy to a higher risk of preterm delivery. To further explore the association, researchers studied 476,489 women who gave birth in the Atlanta metropolitan area between 1994 and 2004. The researchers tracked daily pollution levels using data from various air-quality monitors in five counties.

Three particular air pollutants were found to be related to a higher risk of premature delivery. Specifically, the daily rate of preterm births inched upward when levels of fine particulate matter were elevated over the previous week. The increase was seen among women who lived within 6.5 kilometres of the air-quality monitoring site recording high air pollution levels.

Car exhaust is the prime source of fine particulate matter, but it is also produced by power plants and certain other industrial sources. The particles are small enough to be inhaled deeply into the lungs. The strongest evidence was found for nitrogen dioxide (NO2), a marker of motor vehicle exhaust, being linked to an increase in the daily preterm-birth rate when levels were elevated in the previous six weeks.

The above findings could be attributed to the fact that exposure to air pollution later in pregnancy could activate an inflammatory response in the body that might trigger early labour. The researchers recommended that pregnant women should try to avoid air pollution sources like high-traffic areas.