Gestational diabetes: the significance of persistent fasting hyperglycemia for the subsequent development of diabetes mellitus.

There are little data regarding the temporal pattern of hyperglycaemia during gestational diabetes (GDM) and its significance for the development of future diabetes. The aim of this study was to examine the relationship between fasting and postprandial hyperglycemia in a GDM pregnancy, with the development of subsequent diabetes mellitus (DM). Participants with a history of GDM were identified by a medical records review and invited to be tested for diabetes. One hundred and two participants participated in the study, up to 8 years after their pregnancy. Diabetes had developed in 29%, and 16% had impaired glucose tolerance. Pregnancy factors predictive for the development of diabetes included BMI, the fasting and 2-h BGL on the GTT, and the use of insulin. We used the need for bedtime intermediate-acting insulin as an indicator of persistent fasting hyperglycemia and the need for prandial short-acting insulin as a marker of postprandial hyperglycemia. Compared with participants not treated with insulin, those requiring bedtime insulin had a relative risk of 6.2 (95% CI=2.7-14.1, P<.001) for the development of diabetes. However, participants who required prandial insulin only did not have a higher likelihood of diabetes, compared with those who did not require insulin (relative risk=1.5, 95% CI=0.5-3.8, NS). We conclude that the need for bedtime insulin, reflecting persistent fasting hyperglycemia in a GDM pregnancy, is highly predictive for the development of subsequent DM.