The insulin response to glucose infusion in normal human pregnancy

To study insulin response and insulin sensitivity a glucose infusion test was devised. Twenty normal non-pregnant and twenty normal pregnant women had an intravenous glucose tolerance test followed by a glucose infusion test. In a normal pregnant group at 38-40 weeks gestation (n = 20) the plasma insulin response was found to be 3.7 times greater than that observed in a normal non-pregnant group (n = 20), while in the normal pregnant group the insulin sensitivity index was only 18 per cent of that observed in the non-pregnant group. Intravenous glucose tolerance in the non-pregnant women was observed to correlate with the insulin sensitivity index (r = 0.61, p less than 0.05) but in the pregnant women it correlated with the insulin response (r = 0.66, p less than 0.01). These findings support the hypothesis that in the non-pregnant state intravenous glucose tolerance may be primarily related to insulin sensitivity while during pregnancy it may be related to the degree of compensatory hyperinsulinism.