Diabetes mellitus is one of the most common and important medical complications affecting pregnancy. It can predate the pregnancy ('pre-existing diabetes') or arise during pregnancy ('gestational diabetes', GDM). Typically, GDM resolves once the pregnancy has ended. However, about 3% of women with a diagnosis of GDM have type 2 diabetes diagnosed for the first time in pregnancy, which persists beyond pregnancy. The coexistence of diabetes of any type and pregnancy is associated with an inc...