Background: The purposes of this study were to explore whether the maternal-fetal outcomes differed among various types of hyperglycemia during pregnancy and whether the values of glycemic screening in the middle phase of pregnancy could predict maternal-fetal outcomes. Methods: A retrospective study was conducted to study the incidence of maternal-fetal outcomes in 383 singleton pregnant women with diabetes or gestational diabetes admitted to our hospital from November 2007 to March 2013. Patients were divided into three groups: DM (Type 1 and Type 2 diabetes mellitus) group, mGDM (mild gestational diabetes mellitus) group and sGDM (severe gestational diabetes mellitus) group. Maternal basic characteristics, results of oral glucose tolerance test (OGTT), antenatal random glycemia and maternal-fetal outcomes were collected. Binary logistic regression was used to estimate the association of blood glucose with the maternal-fetal outcomes. Predictive accuracy was assessed by calculating the areas under the receiver operating characteristic curves. Results: The maternal basic characteristics, maternal complications and neonatal complications did not differ significantly between DM group and sGDM group, except neonatal intensive care units admission (NICU). Incidences of preterm, NICU and preeclampsia were significantly lower in the mGDM group than in the DM and sGDM groups (P < 0.05). After adjusted by confounding factors, the value of OGTT 0 h could predict pregnancy induced hypertension (PIH) (OR = 1.24, 95% CI [1.04 to 1.46], P = 0.015), preterm birth (OR = 1.23, 95% CI [1.03 to 1.47], P = 0.025) and stillbirth (OR = 1.55, 95% CI [1.14 to 2.10], P = 0.005); antenatal random glycemia could predict preterm birth (OR = 1.19, 95% CI [1.08 to 1.31], P < 0.001) and stillbirth (OR = 1.41, 95% CI [1.17 to 1.71], P < 0.001). Conclusions: Pregnant women in the mGDM group have better outcomes than those in the DM and sGDM groups. The values of OGTT in the middle phase of pregnancy and antenatal random glycemia could predict PIH, preterm birth or stillbirth to some extent.