[Relationship between low birthweight and air pollution in the city of Sao Paulo, Brazil].

OBJECTIVE Air pollution has been investigated as a potential determinant for low birthweight. The aim of the present study was to study the effect of air pollution on birthweight. METHODS We analyzed all deliveries by mothers living in the municipality of Sao Paulo, Southeastern Brazil, between 1998 and 2000. We estimated the prevalence of low birthweight according to newborn, mother, and delivery characteristics. Only births occurring in the most central districts of the city were analyzed, totaling 311.735 events. For the evaluation of the effects of air pollution, we excluded preterm and multiple deliveries. Pollutants analyzed were ozone (O3), sulfur dioxide (SO2), nitrogen dioxide (NO2), suspended particles (PM10), and carbon monoxide (CO). The effect of maternal exposure to air pollution on birthweight was evaluated using linear and logistic regression. RESULTS A total of 4.6% of newborns weighed less than 2,500 g at birth. Maternal exposure to CO, PM10, and NO2 during the first trimester of pregnancy was significantly associated with decreased birthweight. CONCLUSIONS Our results reinforce the notion that maternal exposure to air pollution during the first trimester of pregnancy may contribute to lesser weight gain in the fetus.