Glucose kinetics in nondiabetic and diabetic women during the third trimester of pregnancy

Abstract

Glucose kinetics were measured with 78% enrichedd-[U-13C] glucose by the prime constant infusion technique during the third trimester of pregnancy in nine nondiabetic women, nine insulin-dependent diabetic women, six gestational diabetic women, and five control women (nonpregnant, nondiabetic) after an overnight fast. The patients not dependent on insulin were diagnosed as diabetic by oral glucose tolerance tests with the use of O'Sullivan and Mahan's criteria as modified by Carpenter and Coustan during the third trimester. The turnover studies were repeated post partum (6 weeks to 5 months after delivery) in 14 of the 24 pregnant subjects. All pregnant groups had a progressive fall in plasma glucose concentration during the study, but there was a steady state of plasma glucose concentration during the turnover period. In comparison to the control subjects, both the pregnant nondiabetic and pregnant insulin-dependent diabetic women had significantly higher plasma insulin concentrations throughout the study (p < 0.05). There were no differences in the glucose turnover rate between any of the pregnant groups (1.7 ± 0.2 mg · kg−1min−1 in pregnant nondiabetic women; 1.5 ± 0.2 mg · kg−1min−1 in pregnant insulin-dependent diabetic women; and 2.1 ± 0.4 mg · kg−1min−1 in gestational diabetic women) and the control group of women (1.8 ± 0.2 mg · kg−1min−1) (mean ± SEM). When the pregnant patients were studied post partum, the glucose turnover rate was similar when referenced to body weight; however, because of a 9.6% to 14.5% fall in weight post partum, the absolute values were higher in the pregnant women. We conclude that, in the basal state after an overnight fast, (1) both nondiabetic and diabetic patients accelerated their glucose turnover rate during pregnancy to provide for increased maternal and fetoplacental metabolic requirements, and (2) in the diabetic subjects the nearly normal plasma glucose and insulin concentrations and other metabolic parameters, as well as the glucose turnover rate, suggested good metabolic control during pregnancy in most of the insulin-dependent and in all of the gestational diabetic patients.