Two-sample Mendelian randomization analyses demonstrated that higher fetuin-A levels were associated with a significantly reduced risk of thoracic aortic aneurysm (odds ratio (OR) = 0.64, 95% confidence interval (CI): 0.47 - 0.87, P = 0.0044) and a decrease in the diameter of thoracic aortic aneurysms (β = -0.086, standard error (SE) = 0.036, P = 0.017). This evidence concerns the gene AHSG and thoracic aortic aneurysm.