Gestational diabetes (GD) is a common complication of pregnancy. Its prevalence depends on the strategy used for screening and the studied population. Pregnant women with GD are at increased risk for maternal and fetal complications. The relationship between maternal blood sugar and complications is linear, without a clear threshold defining GD. Therefore, the diagnostic criteria for GD have been the subject of several controversies since many years. The choice of the one-step or two-step method, the test to be used and the cut-off levels validated to define GD are still debated. The same is true regarding a universal versus a at-risk population screening. International experts have recently proposed the use of a one-step approach with a 2-hour oral glucose tolerance test for a universal screening. The need for a better harmonization regarding the diagnosis of GD is indeed mandatory. The present article discusses both the advantages and disadvantages of the various approaches used for GD screening.