Outdoor air pollution, low birth weight, and prematurity

This study tested the hypothesis, suggested by several recent reports, that air pollution may increase the risk of adverse birth outcomes. This study analyzed all singleton live births registered by the Czech national birth r egister in 1991 in 67 districts where at least one pollutant was monitored in 1990-1991 (n = 108,173). Maternal exposures to sulfur dioxide (SO2), tot al suspended particles (TSP), and nitrous oxides (NOx) in each trimester of pregnancy were estimated as the arithmetic means of all daily measurements taken by all monitors in the district of birth of each infant. Odds ratios of low birth weight (< 2,500 g), prematurity (< 37 weeks of gestation), an d intrauterine growth retardation (IUGR; < 10th percentile of birth weight for gestational age and sex) were estimated by robust logistic regression. The median land 25th and 75th percentile) trimester exposures were 32 (18, 56) mu g/m(3) for SO2; 72 (55, 87) mu g/m(3) for TSP; and 38 (23, 53) mu g/ m(3) for NOx. Low birth weight (prevalence 5.2%) and prematurity (prevalenc e 4.8%) were associated with SO, and somewhat less strongly with TSP. IUGR was not associated with any pollutant. The effects on low birth weight and prematurity were marginally stronger for exposures in the first trimester, and were not attenuated at all by adjustment for socioeconomic factors or t he month of birth. Adjusted odds ratios of low birth weight were 1.20 [95% confidence interval (CI), 1.11-1.30] and 1.15 (CI, 1.07-1.24) for a 50 mu g /m(3) increase in SO2 and TSP, respectively, in the first trimester; adjust ed odds ratios of prematurity were 1.27 (CI, 1.16-1.39) and 1.18 (CI, 1.05- 1.31) for a 50 mu g/m(3) increase in SO2 and TSP, respectively, in the firs t trimester. Low gestational age accounted for the association between SO2 and low birth weight. These Endings provide further support for the hypothe sis that air pollution can affect the outcome of pregnancy.