Gestational diabetes mellitus (GDM) is defined as carbohydrate intolerance of varying degrees of severity with onset or first recognition during pregnancy. The current recommendation is to perform screening test between 24 and 26 weeks of gestation, although there are reports claiming that between 40 and 66% of women with GDM could be detected during early pregnancy (1,2). The policy of screening in the third trimester has resulted in a significant number of pregnant women delivering big babies, despite good glycemic control (3), whereas an early screening for glucose intolerance and care has resulted in the reduction of some of the hyperglycemia-related complications (4). Pregnant women diagnosed as having glucose intolerance in the first trimester are likely to have unrecognized type 2 diabetes before pregnancy (pre-GDM) or pregnancyinduced glucose intolerance during pregnancy (GDM) (5,6). These two clinical situations need to be delineated, as pre-GDM women are likely to have more morbidity and require immediate attention. Hence, we undertook this study to find out whether estimation of A1C levels, along with oral glucose tolerance tests (OGTTs), would help us to distinguish between these two groups, as A1C is directly related to the average concentration of blood glucose in the previous weeks. We also wanted to assess the A1C level during normal pregnancy in our population.RESEARCH DESIGN AND METHODS -We screened 507 consecutive pregnant women for diabetes and pregnancy who were attending our referral center, irrespective of trimesters, with a 75-g OGTT. Women with a history of type 2 diabetes and GDM were excluded from this study. Blood samples were drawn at fasting and at 1 and 2 h for estimating plasma glucose. The plasma glucose was estimated by GOD-POD method using a Hitachi autoanalyzer 902. In the fasting sample, in addition to plasma glucose, A1C and hemoglobin were measured. A1C was estimated by high-performance liquid chromatography (Bio-Rad). Diagnosis of GDM was based on the World Health Organization criteria of a 2-h plasma glucose level Ն140 mg/dl. Details regarding family history, previous obstetric history, treatment for any concomitant diseases, and food habits were obtained. All of the patients underwent routine physical examination.RESULTS -Among the 507 women screened, 255 (50.3%) were in the first trimester of pregnancy. In this group, 86 (33.7%) had GDM (16.96% of the total women screened), and their mean age, BMI, and gestational weeks at screening during the first trimester were 30.63 Ϯ 4.62 years, 25.56 Ϯ 4.00 kg/m 2 , and 9.0 Ϯ 3.03 weeks, respectively. In women with normal glucose tolerance, the mean age, BMI, and gestational weeks at screening during the first trimester were 28.01 Ϯ 4.72 years, 24.48 Ϯ 4.41 kg/m 2 , and 9.45 Ϯ 3.44 weeks, respectively.There was no statistically significant difference among age, BMI, and gestational weeks of the women in the normal glucose tolerant and GDM groups (P Ͼ 0.05). The mean A1C level of the women with normal glucose tolerance was 5.36 Ϯ 0...