Plasma insulin response following intravenous glucose in gestational diabetics.

More insulin is needed to maintain glucose homeostasis during pregnancy. Pregnancy also has a diabetogenic effect on the mother, especially in genetically and obstetrically predisposed women. In the third trimester 195 pregnant women were screened for glucose tolerance by IVGTT (0.33 g/kg body-weight) and for plasma insulin response. In early puerperium the test was repeated. The results in gestational diabetics (k-value less than or equal to 1.0; n = 98) were to be compared to pregnant women with normal glucose tolerance (n = 97). Statistical methods (incl. discriminant analysis) were to verify differences in acute insulin release of the beta-cell and the cumulative insulin response following intravenous glucose. During the third trimester quantitatively more insulin is released when compared with early puerperium both in gestational diabetics and normal subjects (paired t-test p less than 0.01). A quantitative hypofunction of the beta-cells following intravenous glucose in gestational diabetics can be excluded. On the other hand, the most striking findings are a delayed insulin response in the initial phase of secretion (5-10 min) and significantly higher insulin levels during the late phase especially at the end of the test period (60 min) in gestational diabetics. In these cases a peripheral insulin resistance can be discussed. Hyperinsulinism is correlated to the clinical parameters overweight (greater than 10%) and the gaining of at least 12 kg of weight during pregnancy.