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Associations between PM2.5 and risk of preterm birth among liveborn infants
Alman, B., J. Stingone, M. Yazdy, L. Botto, T. DesRoaiers, S. Pruitt, A. Herring, P. Langlois, W. Nembhardt, G. Shaw, A. Olshan, AND Tom Luben. Associations between PM2.5 and risk of preterm birth among liveborn infants. ANNALS OF EPIDEMIOLOGY. Elsevier Science Ltd, New York, NY, 39:46-53.e2, (2019). https://doi.org/10.1016/j.annepidem.2019.09.008
To investigate the relationship between PM2.5 exposure and PTBs, identifying critical windows of exposure, we conducted a case-control analysis, using as our study population controls identified in the nine states involved in the National Birth Defect Prevention Study (NBDPS) from 1999 to 2006.
Recent studies suggest that exposure to ambient particulate matter less than 2.5 μg/m3 in aerodynamic diameter (PM2.5) is associated with increased risk of preterm births (PTB). We investigated the relationship between PM2.5 and PTBs, using singleton controls born from January 1999 through December 2006 participating in the National Birth Defect Prevention Study. PTB was defined as births occurring before 37 weeks gestation. Exposure was assigned using inverse distance weighting of up to 4 monitors within 50 km of maternal residence, accounting for residential mobility when it occurred. To account for state-level variations, including differences in PM composition, a mixed effects logistic regression model was developed with random slopes and intercepts, clustered at the state-level. There were 459 PTBs and 4281 controls included in our analysis. We evaluated household income, maternal education, maternal age, whether the mother was born in the US, maternal race/ethnicity, season of conception, and temperature for potential confounding. In adjusted analyses, PTB was weakly associated with PM2.5 concentrations during the 3rd and 4th months of pregnancy, with no single week of exposure during that time window conveying greater risk of PTB. When we stratified on temperature we found that it modified the relationship between PTB and PM2.5, with higher state-specific temperatures during pregnancy yielding a stronger positive relationship between PM2.5 and PTB. These results add to the literature on the association between air pollution and adverse birth outcomes, and suggest the importance of considering co-exposures, such as temperature when estimating the effects of air pollution exposure during pregnancy.