Impairment of counterregulatory hormone responses to hypoglycemia in pregnant women with insulin-dependent diabetes mellitus.

Intensive insulin therapy directed at elimination of hyperglycemia is advocated during pregnancy in women with insulin-dependent diabetes mellitus. Because such treatment is complicated by frequent hypoglycemic episodes, we evaluated maternal and fetal responses in nine intensively treated pregnant women with insulin-dependent diabetes mellitus during an insulin-induced, gradual, controlled fall in plasma glucose levels. In contrast to values in nonpregnant control women, reductions in glucose to 44 +/- 2 mg/dl in pregnant diabetic patients failed to elicit an increase in glucagon levels. Epinephrine release during hypoglycemia was also markedly suppressed in the pregnant diabetic subjects (106 +/- 32 vs 327 +/- 52 pg/ml in controls, p less than 0.001). Furthermore, the plasma glucose level at which epinephrine and growth hormone were released was 5 to 10 mg/dl lower in the pregnant women with insulin-dependent diabetes mellitus (p less than 0.05). The basal fetal heart rate remained unchanged and continued to manifest accelerations during the hypoglycemic state. We conclude that the high frequency of hypoglycemia in intensively treated pregnant women with insulin-dependent diabetes mellitus may be due in part to impaired counterregulatory hormonal responses.