Diabetes mellitus in a pregnant woman affects the development of the fetal pancreas [2] resulting in hyperinsulinism of the newborn infant who also often presents typical clinical traits [8,23, 32], Furthermore, diabetic women may produce large-for-date infants long before their disturbed carbohydrate metabolism is diagnosed [13,17]. It is not known, however, at which stage in the development of diabetes this effect on the fetus appears. CERASI and LUFT [4,5] have defined "prediabetes" äs a stage in which there is a normal glucose tolerance but a decreased insulin response to glucose infusion (GIT). In a previous study [6] it was demonstrated that in a group of low insulin responders -in which the prediabetic individuals can be expected to be found -the glucose tolerance remained normal throughout pregnancy, while the insulin response increased gradually. The glucose tolerance and insulin response to an intravenous glucose load (IVGTT) of the infants borne by these women and by the control group of high responders were studied. These results together with clinical data on the infants and their mothers are presented here.