Objective: To describe the clinical characteristics, management, and fetal outcomes of patients diagnosed with gestational diabetes mellitus (GDM) or overt diabetes (OD) during pregnancy who followed up at a public healthcare referral center in Brazil. Materials and methods: A retrospective cohort study based on the medical records of women diagnosed with dysglycemia during pregnancy between January 2015 and July 2017 was conducted. Results: Out of 224 pregnant women evaluated, 70% were overweight/obese. GDM was observed in 78.6% of pregnant women, while 21.4% presented with OD. Approximately 59% of patients could be diagnosed with GDM or OD by fasting plasma glucose (FPG) alterations alone. Exclusive diet therapy was used in 50.9% of patients. The need for insulin therapy was higher in OD patients (60.4%) than in GDM patients (38.1%) (p = 0.006). Women who needed insulin (n = 96) had a mean initial dose of 0.33 IU/kg (±0.27) and a final value of 0.39 IU/kg (±0.34). The cesarean rate was 74.3%. The fetal outcomes evaluated were macrosomia (2.15%), large for gestational age (LGA) fetus (15.83%), intensive care unit (ICU) need (4.32%), Apgar score ≤7 (6.47%), hypoglycemia (14.39%) and jaundice (16.55%). Conclusions: Patients with GDM and OD presented with several similar clinical features. Approximately half of the patients presented with adequate glycemic control only with diet management. Patients with OD presented a higher need for insulin therapy. Although overweight and obesity were frequent within both groups, they could possibly explain many of our findings.