INS and diabetes mellitus: Chen and collaborators [4] detected in a prospective study of 408 healthy pregnant women that the glutathione peroxidase (GPx) activity in erythrocytes of the 16th and 30th week of pregnancy, positively correlated with insulin-resistance markers, suggesting a relationship between resistance to insulin and antioxidant defence in a non-diabetic pregnant woman, though it is still unclear which type of relationship exists between diabetes and oxidative stress [5–10].