Gestational Diabetes Mellitus: Levels of Glycemia as Management Goals

Abstract

In the United States, glucose tolerance test criteria for the diagnosis of gestational diabetes mellitus are, in plasma glucose after a 100-g challenge, as follows: fasting, greater than 5.8 mM; 1 h, greater than 10.6 mM; 2 h, greater than 9.2 mM; and 3 h, greater than 8.1 mM; any two values must be elevated. The Second International Workshop-Conference on Gestational Diabetes Mellitus recommended in 1985 that, once diagnosed, women should receive dietary therapy. If fasting or 2-h postprandial hyperglycemia later occurs (fasting, greater than 5.8 mM; 2-h, greater than 6.7 mM), insulin therapy should begin. Data from others have suggested both that the criteria for diagnosis may be too liberal and that the thresholds for instituting insulin therapy may be too high. We address these two issues by reviewing several papers with conflicting conclusions. There is controversy over whether women with gestational diabetes diagnosed by glucose tolerance testing, but who have fasting plasma glucose levels less than 5.8 mM and 2-h postprandial values less than 6.7 mM, should also be insulin treated. Finally, the usual clinical criteria for making therapeutic decisions all rely on glycemia. Other fuels (amino acids, lipids, and ketones) are regulated by circulating insulin and have deleterious effects on fetal development. Further study is required to make more sound clinical decisions based not just on glycemia but on the entire metabolic milieu.