The aim was to find a cost-effective, more practical method to be used in the early gestational weeks as an alternative to the oral glucose tolerance test (OGTT) for predicting gestational diabetes mellitus (GDM). The method selected was adipose tissue measurements made in the first trimester. The study was designed as a prospective, cohort study. Ultrasound images were used to calculate abdominal visceral (VAT) and subcutaneous adipose tissue (SAT) thicknesses of the first trimester pregnant women. Two groups were formed: those who were diagnosed with GDM and those who were not, based on the results of the OGTT performed in the same patients at 24th-28th weeks of gestation. Ultrasonographic records were examined and compared between these two groups using received operator characteristic curves and logistic regression analyses. A total of 292 pregnant women were included, of whom 21.2% were diagnosed with GDM. In the group diagnosed with GDM, SAT, VAT and total adipose tissue (TAT) values were significantly higher than the women who did not have GDM. Threshold values for SAT, VAT and TAT were 18 mm, 55 mm and 55 mm. First trimester SAT, VAT and TAT measurements of pregnant women with GDM were significantly higher than those without GDM diagnosis. Although our results showed that adipose measurements cannot be an alternative to OGTT; they may be a powerful aid in identify at-risk pregnant women, suggesting early OGTT in the first trimester.