Individual Exposure to Nitrogen Dioxide and Preterm Birth Risk in Kaunas

Abstract

Several epidemiological studies have found relationships between exposures to air pollution and adverse birth outcomes, particularly for traffic-related air pollutants, suggesting that the exposure may increase risk of preterm birth. Nitrogen dioxide (NO₂) is the main traffic-related urban air pollutant associated with health effects. The purpose of this study was to assess individual maternal exposure to NO₂ during pregnancy and to study links between the exposure and preterm birth risk in Kaunas, Lithuania. Prospective cohort study comprised all singleton newborns, born to Kaunas citizens in 2008-2009. Case group consisted of 187 preterm births (< 37 weeks), while controls were 3100 term (≥ 37 weeks) singleton newborns. Individual exposure to NO₂ was assigned to each subject during each trimester pregnancy as well as throughout the entire pregnancy by using a dispersion air quality modelling system AIRVIRO. To assess the association between preterm birth and exposure to NO₂ logistic regression analysis was used and odds ratios (OR) and their 95% confidence intervals (95% CI) were calculated. Pregnant women exposed to NO₂ have a slightly increased risk of preterm birth. That risk was shown to be higher when women were exposed to NO₂ levels 24.0-53.2 µg m^-3 during the first and second trimesters, OR 1.21, 95% CI 0.84-1.75 and 1.22, 95%     CI 0.84-1.76, respectively. The study results indicate that residential air pollution might contribute to preterm birth risk.