Impact of maternal exposure to nitrogen dioxide (NO2) during pregnancy on birth weight: a preliminary study in São Paulo, Brazil.

Introduction: Air pollutants have been associated with gestational adverse effects. The aim of this study was to evaluate the impact of maternal exposure to indoor, outdoor and individual nitrogen dioxide (NO2) concentrations during pregnancy on birth weight (BW) in 39 participants. Methods: This study was conduct between 2012 and 2013 in a São Paulo city District, Brazil. These women were recruited with gestational age less than 14 weeks. Indoor, outdoor and individual NO2 concentrations were quarterly measured with passive samplers. A questionnaire was applied to investigate maternal characteristics. Simple and multiple linear regression models were used to estimate the potential maternal risk factors and the contribution of NO2 concentrations to BW. Results: We found a decrease of 374.37g (95%CI -613,21; -135,54) in BW to an increase of one interquartile range (20.02 µg/m3) of indoor NO2 in the third trimester of pregnancy. When other maternal risk factors were included in the multiple linear regression (single, passive smoking, exposure to chemicals during pregnancy, former work in industrial sector, alcoholism and occupation), the effect of NO2 IQR increase in BW remained practically unchanged (-337.52g; 95%CI -628.09; -46.95). Conclusion: These results confirm the impact of NO2 in BW found in studies using ecological data, even though controlling the analysis for several known individual risk factors including passive smoking.