In Argentina, gestational diabetes mellitus (GDM) is diagnosed by the Latin American Diabetes Association (ALAD) diagnostic criterion. In this work, we investigated GDM prevalence according to the ALAD and IADPSG diagnostic criteria, evaluated maternal and fetal outcomes and assessed whether fasting glycemia between 92–99 mg/dL was associated with increased risk of macrosomia and maternal obesity/overweight in an Argentine cohort of pregnant women. GDM prevalence was 9.8% with the ALAD diagnostic criterion and 25% considering the IADPSG criterion. Increased prevalence of maternal obesity/overweight was observed in patients with fasting glycemia over 99 mg/dL. A population of high metabolic risk is identified by the ALAD criterion.