title: [Prenatal exposure to outdoor air pollution and preterm birth: a Meta-analysis].
abstract: OBJECTIVE
  To assess the association between exposure to prenatal outdoor air pollution and preterm birth to provide evidence in setting up programs for prevention on premature birth.
  
  
  METHODS
  Case-control studies regarding association between pregnant exposure to outdoor air pollution and preterm birth were collected. Data were analyzed with Stata 12.0.
  
  
  RESULTS
  Ten articles including 48 556 cases and 548 495 controls were qualified for inclusion. RESULTS from Meta-analyses showed pooled ORs for exposure to NO2, PM10, CO, PM2.5, and NO during the entire pregnancy were 0.960 (95%CI: 0.935-0.985), 1.068 (95%CI: 1.035-1.103), 1.122 (95%CI: 1.078-1.168), 1.110 (95% CI: 1.043-1.181) and 0.994 (95% CI: 0.973-1.016). Association between air pollution and preterm birth varied with the periods of exposure. Pooled ORs for NO2, PM10 and SO2 exposure during the first trimester were 1.117 (95%CI: 1.052-1.186), 0.968 (95%CI: 0.812-1.153) and 1.258 (95%CI: 0.758-2.089). Pooled ORs for NO2, PM10, SO2 exposure during the second trimester were 1.000 (95% CI: 0.982-1.019), 1.127 (95% CI: 0.896-1.416) and 0.977 (95% CI: 0.711-1.342). Pooled ORs for NO2, PM10, SO2 exposure during the third trimester were 1.006 (95%CI: 1.002-1.010), 1.053 (95% CI: 0.973-1.139) and 1.003 (95% CI: 1.000-1.006).
  
  
  CONCLUSIONS
  Exposures to PM10, CO and PM2.5 during the entire pregnancy, to NO2 during the first trimester, or to NO2 and SO2 during the third trimester were associated with preterm births.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Health Science Center of Xi'an Jiaotong University, Xi'an 710061, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.forename: B B
authors.initials: BB
authors.lastname: Mi
authors.forename: Y L
authors.initials: YL
authors.lastname: Zhao
authors.forename: J M
authors.initials: JM
authors.lastname: Yang
authors.forename: Y L
authors.initials: YL
authors.lastname: Tao
authors.forename: H
authors.initials: H
authors.lastname: Yan
mesh_terms: D000393:Air Pollutants; D000397:Air Pollution; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D047928:Premature Birth; D011297:Prenatal Exposure Delayed Effects
chemical_list: D000393:Air Pollutants