Insulin resistance and preeclampsia in gestational diabetes mellitus.

OBJECTIVE: To compare the degree of insulin resistance in women with gestational diabetes mellitus (GDM) who do and do not develop preeclampsia. RESEARCH DESIGN AND METHODS: We conducted a prospective cohort study of initially normotensive women with GDM who underwent oral glucose tolerance tests (OGTTs), intravenous glucose tolerance tests (IVGTTs), and glucose clamp studies in the early third trimester (n = 150) and 15 months postpartum (n = 89). After delivery, the women were categorized as nonpreeclamptic or preeclamptic (systolic blood pressure [SBP] > or = 140 mmHg, diastolic blood pressure [DBP] > or = 90 mmHg, and at least >1+ proteinuria or >300 mg/24 h). Metabolic parameters between the groups were compared by chi2 or Fisher's exact tests and ANOVA with P < 0.05 as significant.
RESULTS: A total of 29 women (19%) developed preeclampsia, which was mild in 21 and severe in 8 women. At entry, there were no differences in age, weight indexes, and glycemic measures between the nonpreeclamptic and preeclamptic groups. Those with preeclampsia were significantly taller (61.5 +/- 2.4 vs. 60.1 +/- 2.3 in, P = 0.003), were more often nulliparous (38 vs. 16%, P = 0.01), and had higher entry SBP (112 +/- 10 vs. 103 +/- 6.9 mmHg, P < 0.0001) and DBP (64 +/- 9 vs. 59 +/- 5 mmHg, P = 0.002). No significant differences between the groups were found in any measures of the OGTT glucose levels, insulin sensitivity index, glucose effectiveness, acute response to glucose, or disposition index, nor were there any differences found in the euglycemic clamp measures of basal or steady-state levels of glucose, insulin, free fatty acid, hepatic glucose output, peripheral glucose clearance, C-peptide, or glucagon. At 15 months postpartum, blood pressure levels remained significantly higher in the preeclamptic group (n = 19) compared with the nonpreeclamptic group (n = 70). No differences in any glycemic or insulin resistance measures were found.
CONCLUSIONS: Women with GDM were uniformly insulin resistant. Those who developed preeclampsia, when compared with those who remained nonpreeclamptic, were not more insulin resistant in either the third trimester or 15 months postpartum. However, women who developed preeclampsia had blood pressure levels that were significantly higher, although still in the normal range, than those of women who remained nonpreeclamptic.