Maternal exposure to low-level air pollution and pregnancy outcomes: a population-based study

BACKGROUND: Recent reports have shown that air pollution may increase the risk of adverse birth outcomes. We have evaluated the relationship between ambient air pollution and the occurrence of low birth weight and preterm delivery using routinely collected data in Lithuania. METHODS: This epidemiological study comprised all singleton newborns (N = 3,988), born to women in 1998, who resided in the City of Kaunas. Birth data and information on maternal characteristics were obtained from the Lithuanian National Birth Register. To estimate residential exposure levels, we used measurements of ambient nitrogen dioxide (NO(2)) and formaldehyde, which were collected at 12 monitoring posts. Multivariate logistic regression was used to estimate the effect that each pollutant would have on low birth weight (LBW) and premature birth while controlling for potential confounders. RESULTS: Adjusted odds ratios (OR) for LBW increased with increasing formaldehyde exposure (OR(2nd tertile )= 1.86, 95% CI 1.10–3.16; OR(3rd tertile )= 1.84, 95% CI 1.12–3.03). Adjusted ORs of preterm birth for the medium and high NO(2 )tertile exposures were OR = 1.14 (95% CI 0.77–1.68) and OR = 1.68 (95% CI 1.15–2.46), respectively. The risk of preterm birth increased by 25% (adjusted OR = 1.25, 95% CI 1.07–1.46) per 10 μg/m(3 )increase in NO(2 )concentrations. An analysis by trimester showed that pregnancy outcomes were associated with first-trimester exposure to air pollutants. However, there were no significant relationships in other pregnancy periods between preterm birth and exposure to formaldehyde or between LBW and NO(2 )exposure. CONCLUSION: Our findings suggest that in the City of Kaunas there might be a relationship between maternal exposure to ambient formaldehyde and the risk of LBW, as well as between NO(2 )exposure and the risk of preterm birth.