INS and type 2 diabetes mellitus: Some studies have shown that it is similar to type 2 diabetes in that the main pathogenesis of GDM is likely to be caused by a decreased insulin secretion and insulin resistance during pregnancy, oxidative stress and inflammatory response, insulin receptor mutations, insulin signal transduction defects, pancreatic β-cell dysfunction that may cause insulin resistance, and the iron overload that may damage pancreatic β-cell, which affects glucose metabolism [9–11].