Abstract: Objective To analyze monitoring data of major air pollutants (sulfur dioxideSO₂,nitrogen dioxideNO₂,particulate mater less than 10 μm in aerodynamic diameterP₁₀) and total and major birth defects in Shenyang from 2006 to 2010,and to explore relationships between various air pollutants and the incidences of birth defects for providing evidences to researches on environmental etiology of birth defects. Methods Concentrations of the three major air pollutants and detection rates of total birth defects and main types the defects in Shenyang city were analyzed with descriptive methods.Ecological methodology was adopted to explore relationships between air pollutant concentrations and incidents of birth defects. Results During the five year period,there were significantly regional differences in the ambient air concentrations of SO₂,NO₂,and PM₁₀(F=149.54,93.39,and 205.69,P<0.05 for all) and there were also significantly seasonal differences in the ambient air concentrations of SO₂,NO₂,and PM₁₀(F=2 035.74,638.10,and 287.41,P<0.05 for all).The concentrations of the three major air pollutants were positively correlated with each other (r=0.517,0.464,and 0.396).There were significant regional differences in detection rates of total birth defect,congenital heart disease,total cleft lip and palate,and other malformations of the external ear (χ²=30.58,14.78,26.74,and 37.25,P<0.05 for all).There were significant seasonal differences in total birth defects,congenital heart disease,total cleft palate,and hemangioma (χ²=240.88,47.44,12.83,and 30.92,P<0.05 for all).The concentrations of the three major air pollutants differed significantly by regions with the highest and the lowest total birth defect detection rate (t=19.36,21.66,and 17.02,P<0.05 for all),and by seasons with higher and lower total birth defect detection rate (t=58.50,41.05,and 27.54,P<0.05 for all).The resulats of Spearman correlation analysis revealed tha PM₁₀ concentration was associated with detection rates of congenital heart disease and hemangioma (r=0.810 and 0.714) and NO₂ concentration was related to the detection rate of hemangioma (r=0.771). Conclusion There are correlations between concentrations of SO₂,NO₂,and PM₁₀ and the detection rate of total birth defect and those of the five major birth defects in Shenyang city.