Glucose tolerance in early pregnancy.

The effect of pregnancy on oral glucose tolerance (50 g of glucose) and plasma insulin and glucagon responses to oral glucose was studied in weeks 10 and 32 of pregnancy and again 1 year post partum in 12 normal women. Already in week 10, fasting plasma glucose was decreased and the glucose-induced insulin secretion increased as compared with post partum. However, glucose tolerance was not affected at this time. In week 32, glucose tolerance had deteriorated, although the levels of both fasting and glucose-induced insulin were higher than those found in early pregnancy and post partum. At all investigations fasting plasma glucagon and the suppression of plasma glucagon after oral glucose were similar, indicating that glucagon is not implicated in the changes in glucose homeostasis seen in pregnancy. It is concluded that glucose tolerance is unaltered by pregnancy in week 10. Pregnancy has, however, at this very early stage already affected glucose homeostasis as seen by the decrease in fasting plasma glucose and the increase in the insulin response to glucose.