title: Residential exposure to traffic and spontaneous abortion.
abstract: BACKGROUND
  Studies have shown associations between air pollution or traffic exposure and adverse birth outcomes, such as low birth weight. However, very few studies have examined the effect of traffic emissions on spontaneous abortion (SAB).
  
  
  OBJECTIVE
  The goal of this study was to determine whether residential exposure to vehicular traffic was associated with SAB.
  
  
  METHODS
  Pregnant women from a prepaid health plan in California were recruited into a prospective cohort study in 1990-1991. Three measures of traffic exposure were constructed for the 4,979 participants using annual average daily traffic (AADT) counts near each residence and distance from residence to major roads. SAB was examined in relation to the traffic exposure measures using logistic regression adjusting for a number of demographic and lifestyle variables.
  
  
  RESULTS
  Of the traffic measures, maximum annual average traffic within 50 m showed the strongest association with SAB, although it was not statistically significant. The adjusted odds ratio (AOR) for the top 90th percentile (AADT greater than 15,199) versus the bottom 75th percentile (AADT = 0-1,089) was 1.18 [95% confidence interval (CI), 0.87-1.60]. However, subgroup analyses showed statistically significant associations for traffic with SAB among African Americans (AOR = 3.11; 95% CI, 1.26-7.66) and nonsmokers (AOR = 1.47; 95% CI, 1.07-2.04).
  
  
  CONCLUSIONS
  In this cohort, living within 50 m of a road with AADT of 15,200 or more was significantly associated with SAB among African Americans and nonsmokers. Further research is needed to confirm these results and possibly elucidate the mechanisms responsible for the findings.
authors.affiliation: Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California 94612, USA. sgreen@oehha.ca.gov
authors.forename: Rochelle S
authors.initials: RS
authors.lastname: Green
authors.forename: Brian
authors.initials: B
authors.lastname: Malig
authors.forename: Gayle C
authors.initials: GC
authors.lastname: Windham
authors.forename: Laura
authors.initials: L
authors.lastname: Fenster
authors.forename: Bart
authors.initials: B
authors.lastname: Ostro
authors.forename: Shanna
authors.initials: S
authors.lastname: Swan
mesh_terms: D000022:Abortion, Spontaneous / Q000209:etiology*; D000293:Adolescent; D000328:Adult; D000397:Air Pollution / Q000009:adverse effects*; D015331:Cohort Studies; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006801:Humans; D018986:Motor Vehicles; D011247:Pregnancy; D011446:Prospective Studies