[Prenatal exposure to outdoor air pollution and preterm birth: a Meta-analysis].

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).

Conclusion: 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.