Poster session II Clinical obstetrics, diabetes, labor, medical-surgical-disease, physiology/endocrinology, prematurity: Abstracts 237 - 386| Volume 208, ISSUE 1, SUPPLEMENT , S110-S111, January 01, 2013

239: Prediction of gestational diabetes mellitus in the first trimester; comparion of fasting plasma glucose, two-step and one-step methods


      Our aim was to determine the best approach in diagnosing gestational diabetes mellitus in the first trimester.

      Study Design

      At the first prenatal visit 736 women between 11-14 weeks underwent fasting blood glucose testing. 486 out of 736 singleton pregnant women who consented to participate were recruited in this randomized prospective study. Women with concomitant diseases, pregestational diabetes or fasting glucose levels >125 mg/dl were excluded. Patients were randomly assigned to two groups; two-step 50-g and a 75-gr glucose challenge test (GCT). In two-step group if the test results exceeded the predefined threshold value (140 mg/dl), the 100-g oral glucose tolerance test (GTT) was performed. In the event of a normal result subsequent testing were performed at 24-28 weeks. Sensitivity, specificity, positive predictive value, negative predictive value, prevalence, positive likelihood ratio and negative likelihood ratios were determined for each group (Table).
      Tabled 1Diagnostic performance of FPG, 50 gr GCT and 75gr GTT in the first trimester
      Table thumbnail grr3


      Among the 486 women studied, 53 women (10.9%) were diagnosed as GDM by American Diabetes Association (ADA) criteria. The fasting plasma glucose (FPG), two step 50gr GCT and 75gr GTT methods identified GDM in 25/486(5.1%), 15/248(6.0%) and 27/238(11.3%) women respectively. Area under ROC curve of FPG testing was 0.623 (95% CI, 0.538-0.707), 50gr two step GCT was 0.708 (95% CI, 0.617-0.798) and 75 gr GTT was 0.792 (95% CI, 0.709-0.876) respectively.


      Fasting plasma glucose levels recommended by The International Association of Diabetes and Pregnancy Study Groups (IADPSG) has a very high false positive rate, making it an inappropriate test for diagnosing GDM. The 75 gr GTT is the preferable test with the highest sensitivity, specificity, positive and negative predicitive values for diagnosing GDM in the first trimester.