Air pollution and very low birth weight infants: a target population?

OBJECTIVE: The goal was to examine systematically the association between maternal exposure to particulate matter of <10 microm and very low birth weight (<1500 g) delivery for evidence of an effect on duration of gestation and/or intrauterine growth restriction. METHODS: This case-control study took place between April 1, 1986, and March 30, 1988, in Georgia Health Care District 9 and included 128 mothers of very low birth weight infants, all of whom were preterm and were classified as either small for gestational age or appropriate for gestational age, and 197 mothers of term, appropriate-for-gestational-age infants weighing > or = 2500 g. Maternal exposure to particulate matter of <10 microm was estimated with 2 exposure measures, namely, a county-level measure based on residence in a county with an industrial point source and an environmental transport model based on the geographic location of the birth home. RESULTS: Considering preterm/appropriate-for-gestational-age infants as cases and term/appropriate-for-gestational-age infants as controls, adjusted odds ratios for maternal exposure to particulate matter of <10 microm were statistically significant (adjusted odds ratio for county-level model: 4.31; adjusted odds ratio for environmental transport model: 3.68). Although elevated, no statistically significant association was found between maternal exposure and preterm/appropriate-for-gestational-age delivery when compared to preterm/small-for-gestational-age delivery. CONCLUSIONS: There are increased odds of maternal exposure to ambient particulate matter of <10 microm for very low birth weight preterm/appropriate-for-gestational-age delivery, compared with term/appropriate-for-gestational-age delivery, which suggests that the observed association between maternal exposure to air pollution and low infant birth weight (particularly <1500 g) is at least partially attributable to an effect on duration of gestation.

Exposures to air pollutants during pregnancy and preterm delivery.

The association between preterm delivery (PTD) and exposure to air pollutants has recently become a major concern. We investigated this relationship in Incheon, Republic of Korea, using spatial and temporal modeling to better infer individual exposures. The birth cohort consisted of 52,113 singleton births in 2001-2002, and data included residential address, gestational age, sex, birth date and order, and parental age and education. We used a geographic information system and kriging methods to construct spatial and temporal exposure models. Associations between exposure and PTD were evaluated using univariate and multivariate log-binomial regressions. Given the gestational age, birth date, and the mother's residential address, we estimated each mother's potential exposure to air pollutants during critical periods of the pregnancy. The adjusted risk ratios for PTD in the highest quartiles of the first trimester exposure were 1.26 [95% confidence interval (CI), 1.11-1.44] for carbon monoxide, 1.27 (95% CI, 1.04-1.56) for particulate matter with aerodynamic diameter < or = 10 microm, 1.24 (95% CI, 1.09-1.41) for nitrogen dioxide, and 1.21 (95% CI, 1.04-1.42) for sulfur dioxide. The relationships between PTD and exposures to CO, NO2, and SO2 were dose dependent (p < 0.001, p < 0.02, p < 0.02, respectively) . In addition, the results of our study indicated a significant association between air pollution and PTD during the third trimester of pregnancy. In conclusion, our study showed that relatively low concentrations of air pollution under current air quality standards during pregnancy may contribute to an increased risk of PTD. A biologic mechanism through increased prostaglandin levels that are triggered by inflammatory mediators during exposure periods is discussed.