Objective To explore the relevant factors influencing the occurrence of gestational diabetes mellitus(GDM)in mid to late pregnancy and their early predictive value for GDM.Methods According to the results of oral glucose tolerance test at 24-28 weeks of pregnancy,99 singleton pregnant women were divided into two groups of GDM(with GDM,45 cases)and C(with normal glucose tolerance,54 cases).The general information,Hb and serum ferritin(SF)in early pregnancy(12 weeks of pregnancy),Hb and FBG in late pregnancy(36 weeks of pregnancy)were compared between the two groups.Multivariate logistic regression analysis was used to analyze the influencing factors for GDM occurrence.ROC curve was used to analyze the early predictive values of BMI,Hb and SF alone and in combination detected in early pregnancy for GDM.Results The weight,BMI in early pregnancy and newborn weight in group GDM were higher than those in group C(P<0.05).The levels of Hb and SF in early pregnancy,Hb and FBG in late pregnancy in group GDM were higher than those in group C(P<0.05).The results of multivariate logistic regression analysis showed that elevated BMI,Hb and SF in early pregnancy were the independent risk factors for GDM in mid to late pregnancy(P<0.05).The AUC values of BMI,Hb,and SF alone and in combination detected in early pregnancy to predict GDM occurrence were 0.708[95%CI(0.600-0.816),P<0.05],0.678[95%CI(0.572-0.784),P<0.05],0.658[95%CI(0.550-0.766),P<0.05],and 0.785[95%CI(0.692-0.877),P<0.05],respectively.Conclusion There is a certain correlation between the increase of BMI,Hb,and SF in early pregnancy and the occurrence of GDM,and the combined detection of the three indicators can improve the predictive value of GDM.