Abstract: OBJECTIVE To investigate the distribution of virulence genes of group B Streptococci (GBS) and the predictive value of 25-hydroxy vitamin D2 (25(OH)D2), chemokine ligand 1 (CCL-1) and antistreptolysin O (ASO) in pregnant women. METHODS Pregnant women with GBS positive cultured from genital tract in Xinxiang Center Hospital from May 2019 to Feb 2022 were recruited as the case group (102 cases), and pregnant women with negative GBS in genital tract during the same period were enrolled as the control group (115 cases). The distribution of virulence genes in pregnant women with GBS positive during pregnancy was analyzed. The serum levels of 25(OH)D2, CCL-1 and ASO as well as pregnancy outcomes were compared between the case group and control group. The serum levels of 25(OH)D2, CCL-1 and ASO in pregnant women with different pregnancy outcomes were compared. Receiver operating characteristic curve (ROC) was used to analyze the predictive value of serum 25(OH)D2, CCL-1 and ASO individual and combinded in the detection of GBS infection in pregnant women. RESULTS The virulence genes detected in 102 GBS positive pregnant women during pregnancy were mainly CAMP, cyl E, and hyl B. The serum level of 25(OH)D2 in the case group was lower than that in the control group (P＜0.05), and the serum levels of CCL-1 and ASO in the case group were higher than those in the control group (P＜0.05). The incidence of amniotic fluid contamination, premature rupture of membranes, premature delivery, fetal distress and neonatal infection in the case group were higher than those in the control group (P＜0.05). The level of serum 25(OH)D2 were lower(P＜0.05). and the levels of serum CCL-1 and ASO were higher in the poor pregnancy outcome group than those in the normal pregnancy outcome group (P＜0.05). The combined detection of serum 25-(OH)VD2, CCL-1, and ASO predicted the area under the curve (AUC) value of GBS infection in pregnant women, which was 0.914. CONCLUSION The virulence genes of GBS in pregnant women mainly include CAMP, cyl E and hyl B. The expression of serum 25(OH)D2 is low, while the expression levels of serum CCL-1 and ASO are high in pregnant women infected with GBS during pregnancy. The combined detection of serum 25(OH)D2, CCL-1 and ASO had higher predictive value for GBS infection in pregnant women.