Ambient air pollution and low birthweight: A European cohort study (ESCAPE)

Background: Ambient air pollution has been associated with restricted fetal growth, which is linked with adverse respiratory health in childhood. We assessed the effect of maternal exposure to low concentrations of ambient air pollution on birthweight. Methods: We pooled data from 14 population-based mother-child cohort studies in 12 European countries. Overall, the study population included 74178 women who had singleton deliveries between Feb 11, 1994, and June 2, 2011, and for whom information about infant birthweight, gestational age, and sex was available. The primary outcome of interest was low birthweight at term (weight <2500 g at birth after 37 weeks of gestation). Mean concentrations of particulate matter with an aerodynamic diameter of less than 25 μm (PM25), less than 10 μm (PM10), and between 25 μm and 10 μm during pregnancy were estimated at maternal home addresses with temporally adjusted land-use regression models, as was PM25 absorbance and concentrations of nitrogen dioxide (NO2) and nitrogen oxides. We also investigated traffic density on the nearest road and total traffic load. We calculated pooled effect estimates with random-effects models. Findings: A 5 μg/m3 increase in concentration of PM25 during pregnancy was associated with an increased risk of low birthweight at term (adjusted odds ratio [OR] 118, 95% CI 106-133). An increased risk was also recorded for pregnancy concentrations lower than the present European Union annual PM25 limit of 25 μg/m3 (OR for 5 μg/m3 increase in participants exposed to concentrations of less than 20 μg/m3 141, 95% CI 120-165). PM10 (OR for 10 μg/m3 increase 116, 95% CI 100-135), NO2 (OR for 10 μg/m3 increase 109, 100-119), and traffic density on nearest street (OR for increase of 5000 vehicles per day 106, 101-111) were also associated with increased risk of low birthweight at term. The population attributable risk estimated for a reduction in PM25 concentration to 10 μg/m3 during pregnancy corresponded to a decrease of 22% (95% CI 8-33%) in cases of low birthweight at term. Interpretation: Exposure to ambient air pollutants and traffic during pregnancy is associated with restricted fetal growth. A substantial proportion of cases of low birthweight at term could be prevented in Europe if urban air pollution was reduced. Funding: The European Union.

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