Objective To investigate the expression level and clinical significance of hsa_circ_0005075 in serum extracellular vesicles(EVs)of patients with recurrent spontaneous abortion(RSA).Methods Fourteen RSA patients and 14 normal pregnant women from the Department of Obstetrics and Gynecology,Qilu Hospital of Shandong University were enrolled in a training set,and 64 RSA pa-tients and 48 normal pregnant women were enrolled in a validation set.The expression levels of hsa_circ_0005075 in serum EVs were detected by the quantitative real-time PCR(qRT-PCR),and their correlation with clinical pathological parameters of RSA patients were analyzed.Serum anti-thyroid globulin antibody(A-TG)and anti-thyroid peroxidase antibody(A-TPO)were detected by the elec-trochemiluminescence assay.Serum anticardiolipin(ACA)IgA,IgG,and IgM antibodies and anti-β2 glycoprotein 1(β2GP1)IgA,IgG,and IgM antibodies were determined by the chemiluminescence immunoassay.The correlation of these autoantibodies with the lev-els of hsa_circ_0005075 in serum EVs was analyzed by the Pearson correlation.The clinical application value of hsa_circ_0005075 in the diagnosis of RSA was evaluated by the receiver operating characteristic(ROC)curve.Results The detection results of the training set showed that the expression levels of hsa_circ_0005075 in serum EVs of RSA patients(7.69[4.74,42.15])were significantly high-er than that in normal pregnant women(1.02[0.51,4.23],U=28,P＜0.01].Similarly,in the validation set,the expression levels of hsa_circ_0005075 in RSA patients(4.96[1.73,8.89])were also significantly higher than that in normal pregnant women(1.00[0.24,2.96],U=693,P＜0.01).The ROC curve showed that hsa_circ_0005075 in serum EVs had good diagnostic value for RSA(AUCROC=0.774),with 70.3%of sensitivity and75.0%of specificity.In addition,the expression level of hsa_circ_0005075 in serum EVs was significantly correlated with A-TPO(r=0.298,P＜0.05).Conclusion The hsa_circ_0005075 in serum EVs is highly ex-pressed in RSA patients,which may have a potential differential diagnostic value for the diagnosis of RSA.