Insulin signalling is a pathway which has been demonstrated to play a major role during pregnancy and in diseases, such as GD, which can have severe effects on the fetus and pregnancy, and long-term effects on both mother and child (e.g., fetal macrosomia, maternal PE, neonatal hyperglycemia, respiratory distress syndrome, and development of type 2 diabetes of the mother after pregnancy, as well as increased risk of obesity and abnormal glucose metabolism of the offspring later in life) [109,110,111]. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.