Gestational diabetes: Should it be added to the syndrome of insulin resistance?

OBJECTIVE - The significance of gestational diabetes mellitus (GDM) results from its short-term detrimental effects on the fetus and its long-term prediction of NIDDM in the mother. We compared several variables associated with insulin resistance between GDM and non-GDM pregnant women to show the similarities between GDM and NIDDM (and thus insulin resistance). RESEARCH DESIGN AND METHODS - On the basis of a 3-h oral glucose tolerance test (OGTT), 52 GDM patients and 127 non-GDM patients were recruited from pregnant, nondiabetic women who had a nonfasting 1-h 50-g glucose screening test greater than or equal to 7.2 mmol/l (130 mg/dl) performed between 16 and 33 weeks of gestation (a total of 518 of 3,041 women drawn from six community health care prenatal clinics were screened positive). During the OGTT, several potential markers of insulin resistance were measured at fasting and 2-h time points, in addition to the standard glucose measurements. The relationship of these variables with the diagnosis of GDM was studied. RESULTS - GDM patients, compared with non-GDM patients, had 1) higher prepregnancy weight (P = 0.011), prepregnancy BMI (P = 0.006), C-peptide at fasting (P = 0.002) and at 2 h (P < 0.001), insulin at fasting (P = 0.001) and at 2 h (P < 0.001), triglycerides at fasting (P = 0.005) and at 2 h (P = 0.003), free fatty acids at fasting (P = 0.017), beta-hydroxybutyrate at fasting (P = 0.007); and 2) lower HDL cholesterol at fasting (P = 0.029). These variables were all predictive of GDM (P < 0.036) individually. Using stepwise logistic regression with all of these variables available, fasting (P = 0.019) and 2-h (P < 0.001) insulin levels, fasting free fatty acids (P = 0.031), and fasting beta-hydroxybutyrate (P = 0.036) were statistically significant as jointly predictive of GDM. Comparisons between GDM patients and non-GDM patients matched by BMI confirmed that the metabolic abnormalities persisted when difference in BMI was taken into account. Concomitant blood pressure measurements in women with GDM did not differ significantly from those without GDM. CONCLUSIONS - Our results show that many of the known metabolic components of the syndrome of insulin resistance (syndrome X) are predictive of GDM. These results are in keeping with the argument that GDM is one phase of the syndrome of insulin resistance. We suggest that GDM be looked upon as a component of the syndrome of insulin resistance that provides an excellent model for the study and prevention of NIDDM in a relatively young age-group.