Characteristics of abnormal oral glucose tolerance test in GDM diagnosis and clinical correlation

Objectives: To describe the characteristics of abnormal oral glucose tolerance test (OGTT) values at gestational diabetes mellitus (GDM) diagnosis and their associations with clinical characteristics, and to evaluate the effect on GDM diagnosis if any OGTT value was omitted. Materials and methods: A cross-sectional study was conducted in 415 women diagnosed with GDM. The OGTT results were recorded and analyzed. Results: Of the 415 included women, mean gestational age at GDM diagnosis was 19.2 weeks and 57.6% were diagnosed before 20 weeks. The highest proportions of abnormal values were found at the 1st and 2nd hour (85.3% and 96.6%, respectively). If the 3rd hour OGTT value was omitted, 16.7% of GDM cases would be missed. Number of abnormal OGTT values and abnormal FPG were significantly associated with obesity. Only pre-pregnancy overweight and obesity independently associated with insulin requirement (adjusted OR: 2.28, 95%CI: 1.02–5.06; p =.044; and adjusted OR: 6.29, 95%CI: 2.67–14.85; p <.001, respectively). Conclusions: Over half of the GDM women had three or four abnormal OGTT values. Omission of the 3rd hour OGTT value would result in 16.7% of patients not being diagnosed with GDM. Number of abnormal OGTT values and abnormal FPG were associated with obesity, and insulin requirement was associated with pre-pregnancy overweight and obesity.