Objective: Gestational diabetes mellitus is a common disorder of carbohydrate metabolism, with onset or first recognition during pregnancy, resulting in hyperglycemia of variable severity. Insulin resistance and chronic subclinical inflammation are the underlying mechanisms of the disease. Soluble interleukin-2 receptor, neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratio are the markers of inflammatory disease processes such as type 1 and 2 diabetes mellitus, hepatitis, and neoplasms.Study Design: In our study, we measured complete blood count, serum soluble interleukin-2 receptor, serum glucose in blood samples from 52 women with gestational diabetes mellitus and 50 pregnant women with normal glucose tolerance. Pregnant women which were tested for oral glucose tolerance test (75 gr load) between 24 and 28 weeks of pregnancy were selected for the study. Gestational diabetes mellitus was defined according to the criteria provided by the National Institute for Health and Care Excellence.Results: In terms of age, gestational diabetes mellitus patients (mean±SD; 31±6 years) were older than controls (mean±SD; 25±5.3 years). Mean platelet volume values were lower in gestational diabetes mellitus patients (mean±SD; 10.3±1.4 fL) as compared to normal glucose tolerance group (mean±SD; 10.8±1fL). No statistically significant differences in serum glucose concentration, white blood cell count, neutrophil count, lymphocyte count, hemoglobin concentration, platelet count, neutrophil-to-lymphocyte ratio value, platelet-to-lymphocyte ratio value, and serum soluble interleukin-2 receptor concentration were found.Conclusion: This study did not reveal an increase in the inflammatory markers, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio and serum soluble interleukin-2 receptor, in gestational diabetes mellitus. The mean platelet volume values were observed to be lower in gestational diabetes mellitus patients.