Objective: The aim of this study is to identify the first trimester markers that may be associated with gestational diabetes mellitus (GDM) and to evaluate whether those markers might be used for prediction of gestational diabetes or not. Methods: Pregnant women between 11 and 14 weeks of gestation applying to the university hospital between August 2018 and March 2019 were included in the study. Body mass index calculation and blood tests including complete blood count, TSH, T3, T4, HbA1c, uric acid, CRP, procalcitonin, PAPP-A and b-hCG levels were done during assessment followed by 50 grams of glucose challenge test between the 24 and 28 weeks of gestation for each woman. Patients with positive results were further evaluated with a 3-hour, 100-g OGTT. According to the diagnostic test results, the relationship between biochemical markers during the first trimester, BMI and GDM was statistically analyzed. Results: A hundred and eighty-two pregnant women participated in the study. Fifty-four women had positive glucose challenge test (GCT) results while 128 women had negative results. Pregnant women with positive GCT results underwent 3-hour, 100-g OGTT and, 24 pregnant women were diagnosed with GDM, while 158 pregnant women were considered healthy according to the results. There was no statistically significant difference between GDM and non-GDM groups in terms of age, height, TSH, T3, T4, b-hCG-mom, PAPP-A, PAPP-A-mom, uric acid and procalcitonin (p>0.05). The mean body weight, body mass index and HbA1c levels were higher and b-hCG levels were lower in the GDM group compared to the non-GDM group, and these findings were statistically significant (p<0.001). Conclusion: The use of first trimester markers in GDM prediction seems to have no significance. There is a need for extensive, randomized studies with universal criteria.