Estimating the risk after gestational diabetes mellitus: can we improve the information from the postpartum OGTT?

Risk stratification after pregnancy with gestational diabetes mellitus (GDM) is based on screening with the 2-h oral glucose tolerance test (OGTT). Actually, prediabetes and diabetes are diagnosed by impaired fasting [fasting plasma glucose (FPG)] and 120 min-postload glucose levels (120'-PLG). We hypothesized that the clinical information could be improved by including measurements at different time points from the OGTT in the medical decision-making process. One hundred ten women with previous gestational diabetes (pGDM) and 41 controls were included 3-6 mo after delivery and underwent specific metabolic assessments: 3-h OGTT, frequently sampled intravenous glucose tolerance test (FSIGT) with markers of inflammation and endothelial function. pGDMs were annually invited for reexaminations for a maximum of 10 yr. Multiple linear regression suggested that postload glucose levels at 60 min (60'-PLG) were a better predictor for insulin sensitivity [β: -0.10, 95% confidence interval (CI) -0.14 to -0.05, P < 0.001] and disposition index (DI) (β: -0.07, 95% CI -0.12 to -0.02, P = 0.004) estimated from the FSIGT compared with other time points during the OGTT. The association between 60'-PLG and insulin secretion was of particular importance in women after GDM. We further identified associations of 60'-PLG with ultrasensitive C-reactive protein, plasminogen activator inhibitor 1, tissue plasminogen activator, endothelial-leukocyte adhesion molecule 1, and intercellular adhesion molecule (ICAM)-1. There appeared to be no interactions between females with pGDM and controls, suggesting comparable effects. We observed that 60'-PLG levels were closely related to the later onset of diabetes independent from the routinely measured FPG and 120'-PLG levels. Our data suggest that the sole interpretation of FPG and 120'-PLG of the OGTT leads to significant loss of information. Particularly 60'-PLG was shown to distinguish women at low or high metabolic and cardiovascular risk.