Evidence is provided for the impermeability of the human placenta for bovine insulin at term. Women in labor received glucose infusions with and without insulin added; the dosage was 1 g glucose and 0.33 units insulin per min. The insulin in cord blood was nearly always elevated after maternal infusions compared with controls, but no difference in fetal insulin concentrations were observed whether insulin was added to mother's infusion or not. Even an 18-fold increase of the maternal insulin level did not affect the insulin level in cord blood. The additional glucose transferred to the fetus by maternal infusion stimulates the fetal insulin secretion with a delay of at least 22 min.
Insulin - Human Placenta - Glucose Infusions - Fetal Insulin - Insulin Stimulation
