In most countries a selective screening is carried out, using parameters such as previous GDM, previous large for gestational age babies, diabetes (of any kind) in first degree relatives, pre-pregnancy adipositas, belonging to a particular ethnic group associated with a high prevalence of GDM, glucosuria, and high maternal age. By using selective screening there is a risk of missing GDM cases. On the other hand, selective screening could help to concentrate medical resources on subjects with the highest risk of complications.