Air pollution and low birth weight: a historical cohort study from Tehran.

This historical cohort study was designed to clarify the association between air pollution and low birth weight (LBW) amongst women referred to Tehran hospitals in 2007. In total, 225 eligible pregnant women who lived within 5 km of an air pollution monitoring station during their pregnancy were selected for the study. Data were collected via interview and hospital records. Exposure to each pollutant was estimated for each woman individually throughout her pregnancy and for each trimester. Exposures were modelled as categorical variables using inter-quartile ranges in a logistic regression model. The results showed a significant association between exposure to CO and LBW (OR = 2.08, 95% Cl: 1.70-4.60), particularly during the second trimester (OR = 3.96, Cl: 1.83-12.5). We conclude that exposure to air pollution during pregnancy may be associated with LBW.