© 2022, Yuzuncu Yil Universitesi Tip Fakultesi. All rights reserved.Gestational Diabetes Mellitus (GDM) is a metabolic condition that develops during pregnancy and is associated with complications. This studies aim was to evaluate and measure the oxidative stress markers and antioxidants levels in women with gestational diabetes and compare them with healthy pregnant women. There were 77 pregnant women who participated in this case-control study. Forty female patients diagnosed with GDM participated in the study as the case group and 37 healthy women as the control group. All biochemical analyzes (IMA, MDA, GSH, CAT) were performed using the spectrophotometric method. When comparing the two groups, the patients group’s serum IMA levels (1.531±0.407 AbsU) were higher than those of the control group’s (0.863 ±0.092 AbsU) (p<0.001). Similarly, the patient group’s MDA levels (1.769 ±0.357 μmol/L) were higher than the control group’s (1.025 ±0.018 μmol/L) (p<0.001). Conversly, the patient group’s GSH levels (0.023 ±0.014 mmol/g) were lower than those of the control group’s (0.186 ±0.012 mmol/g) (p<0.001). This study als o found that both groups’ CAT activity levels had no significant statistical difference (GDM-0.072±0.019 and Control-0.075±0.013 U/L) (p<0.395). These results suggest that while the oxidative stress increased, the antioxidant defense levels decreased in wo men with GDM. It is recommended that patients with GDM are strictly monitored throughout pregnancy, which may help in the management of oxidative stress together with glycemic control.