BACKGROUND Data regarding the effects of multifetal pregnancy on the incidence of gestational diabetes mellitus (GDM) are inconsistent and even conflicting. Twin pregnancies have been associated with no increase, a marginal increase or a higher incidence of gestational diabetes. In triplet pregnancies, these effects have not been investigated yet. OBJECTIVE To analyze the results of the glucose challenge and tolerance tests in singleton, twin and triplet pregnancies. METHODS A retrospective database analysis of pregnant women with singletons, twins or triplets who had complete results of the 50 g glucose challenge test (GCT) and the 100 g oral glucose tolerance test (OGTT). The cohort included 12,382 singletons, 515 twins and 39 triplets. RESULTS There were significantly higher rates of abnormal GCTs in twins and triplets compared to singletons (45.4% and 33.3%, respectively vs. 13.7%, P<0.001 and P<0.05). Significantly higher rates of gestational diabetes in twins (10.1% vs. 2.9 %, P<0.001) and triplets (12.8% vs. 2.9%, P<0.05) compared to singletons were observed. Mean glucose levels after the GCT were higher in twins compared to singletons, and even more in triplets (108 mg/dL in singletons vs. 120 mg/dL in twins vs. 129 mg/dL in triplets, P<0.001). CONCLUSIONS Glucose intolerance is aggravated in multifetal pregnancies. The likelihood of an abnormal GCT and gestational diabetes is higher in twins and triplets compared to singletons.