title: Traffic-related air pollution and risk of preterm birth in the San  Joaquin Valley of California.
abstract: OBJECTIVE
  To evaluate associations between traffic-related air pollution during pregnancy and preterm birth in births in four counties in California during years 2000 to 2006.
  
  
  METHODS
  We used logistic regression to examine the association between the highest quartile of ambient air pollutants (carbon monoxide, nitrogen dioxide, particulate matter <10 and 2.5 μm) and traffic density during pregnancy and each of five levels of prematurity based on gestational age at birth (20-23, 24-27, 28-31, 32-33, and 34-36 weeks) versus term (37-42 weeks). We examined trimester averages and the last month and the last 6 weeks of pregnancy. Models were adjusted for birthweight, maternal age, race/ethnicity, education, prenatal care, and birth costs payment. Neighborhood socioeconomic status (SES) was evaluated as a potential effect modifier.
  
  
  RESULTS
  There were increased odds ratios (ORs) for early preterm birth for those exposed to the highest quartile of each pollutant during the second trimester and the end of pregnancy (adjusted OR, 1.4-2.8). Associations were stronger among mothers living in low SES neighborhoods (adjusted OR, 2.1-4.3). We observed exposure-response associations for multiple pollutant exposures and early preterm birth. Inverse associations during the first trimester were observed.
  
  
  CONCLUSIONS
  The results confirm associations between traffic-related air pollution and prematurity, particularly among very early preterm births and low SES neighborhoods.
authors.forename: Amy M
authors.initials: AM
authors.lastname: Padula
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Mortimer
authors.forename: Ira B
authors.initials: IB
authors.lastname: Tager
authors.forename: S Katharine
authors.initials: SK
authors.lastname: Hammond
authors.forename: Frederick W
authors.initials: FW
authors.lastname: Lurmann
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.forename: David K
authors.initials: DK
authors.lastname: Stevenson
authors.forename: Gary M
authors.initials: GM
authors.lastname: Shaw
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000032:analysis / Q000633:toxicity*; D000397:Air Pollution / Q000009:adverse effects*; D001724:Birth Weight / Q000187:drug effects; D002140:California / Q000453:epidemiology; D002248:Carbon Monoxide / Q000032:analysis / Q000633:toxicity; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D008423:Maternal Age; D018811:Maternal Exposure; D009589:Nitrogen Oxides / Q000032:analysis / Q000633:toxicity; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D047928:Premature Birth / Q000139:chemically induced* / Q000453:epidemiology; D012111:Residence Characteristics; D018570:Risk Assessment; D001335:Vehicle Emissions / Q000032:analysis / Q000633:toxicity*; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D009589:Nitrogen Oxides; D052638:Particulate Matter; D001335:Vehicle Emissions; D002248:Carbon Monoxide