Glucose metabolism during and after pregnancy in normal and gestational diabetic women. 1. Influence of normal pregnancy on serum glucose and insulin concentration during basal fasting conditions and after a challenge with glucose.

Glucose and insulin concentrations during basal fasting conditions and after an oral challenge with glucose have been studied during early, mid and late pregnancy and also after delivery in a group of 9 normal women. No significant changes in the fasting serum glucose concentration was observed during pregnancy. In contrast the fasting serum insulin gradually increased. No changes in the mean glucose concentration curve were observed until the second half of pregnancy where the level of the curve was significantly elevated, but statistically calculated limits of normality derived from a special study of non-pregnant normal controls were not exceeded. The serum insulin response to glucose was significantly increased at all stages of gestation and in parallel the insulin-to-glucose index calculated for the total areas below the insulin and glucose concentration curves increased significantly. The fasting insulin-to-glucose index also increased and was found to be significantly correlated to the stage of gestation. The shape of the glucose and insulin curves was modified in the opposite direction by pregnancy: the peak value of glucose was delayed whereas that of insulin was advanced. The results indicate that in pregnancy a diminished "peripheral sensitivity" to endogenous insulin apparently develops.