In conclusion, pregnant Algerian women with GDM included in this study, were seleno-deficient, their supplementation with Se (50 μg/d for 12 weeks) from their second trimester of pregnancy, resulted in the best manifestation of its insulin-mimetic and antioxidant properties that led to an improvement in carbohydrate metabolism expressed by significant decrease in FPG level, a strengthening in selenodependent antioxidant defense, a recovery of SOD and CAT activities and a significant decrease in plasma and erythrocyte MDA levels and plasma PC level. Here, CAT is linked to gestational diabetes.