The mammalian fetus develops inside the uterus of its mother and is completely dependent on the nutrients supplied by its mother. Disturbances in the maternal metabolism that alter this nutrient supply from mother to fetus can induce structural and functional adaptations during fetal development, with lasting consequences for growth and metabolism of the offspring throughout life. This effect has been investigated, by several research groups, in different experimental models where the maternal metabolism during pregnancy was experimentally manipulated (maternal diabetes and maternal malnutrition) and the effect on the offspring was investigated. The altered maternal/fetal metabolism appears to be associated with a diabetogenic effect in the adult offspring, including gestational diabetes. This diabetic pregnancy in the offspring again induces a diabetogenic effect into the next generation, via adaptations during fetal development. These experimental data in laboratory animals are confirmed by epidemiological studies on infants of mothers suffering from diabetes or malnutrition during pregnancy. It can be concluded that fetal development in an abnormal intra-uterine milieu can induce alterations in the fetal metabolism, with lasting consequences for the glucose tolerance of the offspring in adult life. The most marked effect is the development of gestational diabetes, thereby transmitting the diabetogenic tendency to the next generation again. The concept of fetal origin of adult diabetes therefore is of major significance for public health in the immediate and the far future.