Twenty-eight healthy women, 17 with high and 11 with low insulin response to glucose but with normal glucose tolerance, were followed throughout pregnancy. Plasma FFA, glycerol and D-beta-hydroxybutyrate as well as plasma insulin and glucose in blood were determined before and during a glucose infusion test (GIT) in each trimester and after pregnancy. In 13 infants of high insulin responders (IHR) and 10 infants of low responders (ILR) an intravenous glucose tolerance test (IVGTT) was performed, and the above lipid parameters were studied at birth and during the IVGTT. The low responder group was postulated to consist mainly of prediabetic individuals (8). Their infants have previously been shown to have an increased glucose assimilation rate at IVGTT (12, 13), as has been shown for infants of diabetic mothers. There was little difference between the two groups of mothers except for the insulin levels during the GIT in non-pregnant and early pregnant subjects, which were considerably lower in the low responders. They all had decreased fasting levels of FFA, glycerol, and D-beta-hydroxybutyrate in mid-pregnancy and normal values in late pregnancy. The ILR showed the same changes in FFA and glycerol as the IHR, but their D-beta-hydroxybutyrate levels were higher at birth than those of the IHR and lower after birth. Another difference found, was the correlation between birth weight and fasting insulin (and to some extent the insulin level at birth) in the ILR group, which was not found in the IHR. Apart from those differences the ILR and the IHR seemed to handle their fat metabolism in a similar way in the early neonatal perinatal period.