title: The International Collaboration on Air Pollution and Pregnancy Outcomes: initial results.
abstract: BACKGROUND
  The findings of prior studies of air pollution effects on adverse birth outcomes are difficult to synthesize because of differences in study design.
  
  
  OBJECTIVE
  The International Collaboration on Air Pollution and Pregnancy Outcomes was formed to understand how differences in research methods contribute to variations in findings. We initiated a feasibility study to a) assess the ability of geographically diverse research groups to analyze their data sets using a common protocol and b) perform location-specific analyses of air pollution effects on birth weight using a standardized statistical approach.
  
  
  METHODS
  Fourteen research groups from nine countries participated. We developed a protocol to estimate odds ratios (ORs) for the association between particulate matter ≤ 10 μm in aerodynamic diameter (PM₁₀) and low birth weight (LBW) among term births, adjusted first for socioeconomic status (SES) and second for additional location-specific variables.
  
  
  RESULTS
  Among locations with data for the PM₁₀ analysis, ORs estimating the relative risk of term LBW associated with a 10-μg/m³ increase in average PM₁₀ concentration during pregnancy, adjusted for SES, ranged from 0.63 [95% confidence interval (CI), 0.30-1.35] for the Netherlands to 1.15 (95% CI, 0.61-2.18) for Vancouver, with six research groups reporting statistically significant adverse associations. We found evidence of statistically significant heterogeneity in estimated effects among locations.
  
  
  CONCLUSIONS
  Variability in PM₁₀-LBW relationships among study locations remained despite use of a common statistical approach. A more detailed meta-analysis and use of more complex protocols for future analysis may uncover reasons for heterogeneity across locations. However, our findings confirm the potential for a diverse group of researchers to analyze their data in a standardized way to improve understanding of air pollution effects on birth outcomes.
authors.affiliation: National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, Maryland 20782, USA. jdparker@cdc.gov
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Parker
authors.forename: David Q
authors.initials: DQ
authors.lastname: Rich
authors.forename: Svetlana V
authors.initials: SV
authors.lastname: Glinianaia
authors.forename: Jong Han
authors.initials: JH
authors.lastname: Leem
authors.forename: Daniel
authors.initials: D
authors.lastname: Wartenberg
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Bell
authors.forename: Matteo
authors.initials: M
authors.lastname: Bonzini
authors.forename: Michael
authors.initials: M
authors.lastname: Brauer
authors.forename: Lyndsey
authors.initials: L
authors.lastname: Darrow
authors.forename: Ulrike
authors.initials: U
authors.lastname: Gehring
authors.forename: Nelson
authors.initials: N
authors.lastname: Gouveia
authors.forename: Paolo
authors.initials: P
authors.lastname: Grillo
authors.forename: Eunhee
authors.initials: E
authors.lastname: Ha
authors.forename: Edith H
authors.initials: EH
authors.lastname: van den Hooven
authors.forename: Bin
authors.initials: B
authors.lastname: Jalaludin
authors.forename: Bill M
authors.initials: BM
authors.lastname: Jesdale
authors.forename: Johanna
authors.initials: J
authors.lastname: Lepeule
authors.forename: Rachel
authors.initials: R
authors.lastname: Morello-Frosch
authors.forename: Geoffrey G
authors.initials: GG
authors.lastname: Morgan
authors.forename: Rémy
authors.initials: R
authors.lastname: Slama
authors.forename: Frank H
authors.initials: FH
authors.lastname: Pierik
authors.forename: Angela Cecilia
authors.initials: AC
authors.lastname: Pesatori
authors.forename: Sheela
authors.initials: S
authors.lastname: Sathyanarayana
authors.forename: Juhee
authors.initials: J
authors.lastname: Seo
authors.forename: Matthew
authors.initials: M
authors.lastname: Strickland
authors.forename: Lillian
authors.initials: L
authors.lastname: Tamburic
authors.forename: Tracey J
authors.initials: TJ
authors.lastname: Woodruff
mesh_terms: D000397:Air Pollution / Q000009:adverse effects* / Q000706:statistics & numerical data; D001724:Birth Weight; D015331:Cohort Studies; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007391:International Cooperation; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity*; D010865:Pilot Projects; D011247:Pregnancy; D011256:Pregnancy Outcome; D047928:Premature Birth / Q000139:chemically induced* / Q000453:epidemiology; D012107:Research Design; D012307:Risk Factors; D012959:Socioeconomic Factors
chemical_list: D052638:Particulate Matter