Recent Italian guidelines exclude women <35 years old, without risk factors for gestational diabetes mellitus (GDM), from screening for GDM. To determine the effectiveness of these measures with respect to the International Association of the Diabetes and Pregnancy Study Groups (IADPSG) criteria, we evaluated 2,448 pregnant women retrospectively enrolled in Calabria, southern Italy. GDM was diagnosed following the IADPSG 2010 criteria. Among 538 women <35 years old, without risk factors, who would have not been tested according to the Italian guidelines, we diagnosed GDM in 171 (31.8%) pregnants (7.0% of total pregnants). Diagnosis was made at baseline (55.6%), 1 hour (39.8%), or 2 hours (4.7%) during OGTT. Despite of appropriate treatment, GDM represented a risk factor for cesarean section, polyhydramnios, increased birth weight, admission to neonatal intensive care units, and large for gestational age. These outcomes were similar to those observed in GDM women at high risk for GDM. In conclusion, Italian recommendations failed to identify 7.0% of women with GDM, when compared to IADPSG criteria. The risk for adverse hyperglycaemic-related outcomes is similar in low-risk and high-risk pregnants with GDM. To limit costs of GDM screening, our data suggest to restrict OGTT to two steps (baseline and 1 hour).