Comparison the Carpenter and Coustan thresholds with the new thresholds obtained from Thai pregnant women for the diagnosis of gestational diabetes

AimsTo determine the threshold of plasma glucose levels calculated from the mean + 2SDs for diagnosing gestational diabetes mellitus (GDM) in Thai women.MethodsThai pregnant women without pre-existing diabetes were invited into the study. A 100-g oral glucose tolerance test (OGTT) was performed in all participants during their second or third trimesters, regardless of the results of 50-g glucose challenge test.ResultsSeven hundred and ninety seven women with singleton pregnancy participated in the study. The distribution of 1-, 2-, and 3-h plasma glucose levels of the 100-g OGTT was Gaussian. The rounded cut-off point values calculated from the mean + 2SDs were 90, 195, 170, and 155 mg/dl, respectively for fasting, 1-, 2-, and 3-h plasma glucose. With the Carpenter and Coustan thresholds, 52 women (6.5%, 95%CI 4.9–8.5%) were diagnosed as GDM. Of these, when tested with the new thresholds, 30 had normal glucose tolerance and 22 were diagnosed as GDM.ConclusionBy using mean + 2SDs of plasma glucose levels of the 100-g OGTT as the threshold for diagnosing GDM, the thresholds at 1, 2, and 3 h obtained from Thai women were 15 mg/dl higher than those of the Carpenter and Coustan thresholds.