Objective: The study aims to compare alterations of glucose fluctuations across individuals with different kinds of diabetes in pregnancy and investigate influencing factors that may react with glucose variations (GV). Design：A retrospective cohort study was conducted from May 2018 and May 2021. Setting：Shanghai General Hospital. Population: A total of 776 pregnant women who were diagnosed diabetes was obtained. We grouped participants who were exposed to gestational hyperglycemia into 5 sub-groups [Type 1 diabetes (T1DM), Type 2 diabetes (T2DM), Overt diabetes, Gestational diabetes (GDM) 1 and GDM2). Methods: Logistic regression models, one way Analysis of Variance (ANOVA) method and the chi-squared test were utilized. Main Outcome Measures: Demographic variables and GV parameters were compared among 5 groups through ANOVA-test and Chi-square test. We estimated odd ratios (ORs) for the association between glucose coefficient of variation (CV) and possible influencing variables. Results: T1DM group performed greatest glucose fluctuations with a CV value 35.02% whereas the number in all the other groups was no more than 22.82%. On multivariate logistic regression analysis of possible factors influencing CV, only body mass index (BMI) (OR: 0.754, P=0.029), HOMA- β (OR:0.969, P=0.037) and fasting plasma glucose (FPG) (OR: 1.832, P=0.008) reached statistical significance. Conclusions: A greater GV in pregnant women with pre-pregnancy diabetes than that in GDM controls, and the former had a worse glucose profile than the other two groups while ODM group coming second. BMI, HOMA-β and FPG remain as an independent risk factors for unstable GV.