Research published in the British Journal of Obstetrics and Gynaecology (2006;113:935–941) analyzed data from more than 28,000 births in Brisbane, Australia. Investigators estimated maternal exposure to air pollution—including ozone, nitrogen dioxide, and particulate matter (PM10)—during both the first and last trimesters of pregnancy.
During the study period, 5.6% of births occurred before 37 weeks’ gestation, the threshold used to define preterm birth. Preterm births were more common during the winter months. Higher ozone exposure was associated with a 26% increase in the risk of preterm birth, while increased exposure to PM10 during the first trimester was associated with a 15% increase in preterm births.
