Accumulating evidence indicates that maternal exposures to air pollutants including O3, CO, PM10, and SO2 are associated with adverse pregnancy outcomes. Exposures to CO and PM10 during the first month and third trimester have been associated with reduced birth weight. The effects of O3 exposure on birth weight have not been as extensively studied. To determine whether prenatal exposure to air pollution is associated with reduced birth weight we examined birth weight and prenatal exposures among participants in the CHS born in California from 1975–1987. Air pollution data obtained from the Environmental Protection Agency’s (EPA) Aerometric Information Retrieval System (AIRS) and inverse distance weighted interpolation was used to assign prenatal exposure based on zip codes of the maternal birth residences of the 3901 California-born subjects with gestational ages from 37 to 44 weeks. Mixed effects models were fitted to estimate the effects of O3, PM10, NO2, and CO on birth weight obtained from California birth certificates after adjusting for gestational age, maternal age, sex, race of subject, time since last live birth, parity, study cohort, maternal smoking during pregnancy, socioeconomic status, marital status, and diabetes-related pregnancy complications. Ozone (24 hr average), averaged over the entire pregnancy, as well as exposures restricted to the second and third trimester periods, were associated with reduced birth weight.
CO and PM10 were also significantly associated with reduced birth weight in the first and third trimesters, respectively. No associations were observed for NO2. This analysis provides evidence that prenatal exposure to O3, PM10, and CO is associated with reduced birth weight in full term infants.