Pre-pregnancy excessive weight, excessive gestational weight gain and GDM are associated with: infants large for gestational age, high birth weight, andmacrosomia.16-19 Pregnant women with GDM have a reduction in the peripheral insulin sensitivity, leading to maternal hyperglycemia, fetal hyperglycemia, and consequent hyperinsulinemia, resulting in excessive fetal growth.34 Obesity , in turn, has a significant effect on the macronutrient metabolism, altering glucose homeostasis, lipid oxidation, and amino acid synthesis, resulting in a possible interference with the fetus development.35 The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.