Welcome to HCM.
IGT means Impaired Glucose Tolerance
leading to GDM. It has various ill effects on baby if not controlling like big baby,heart defect etc.
Your first son was also big enough (8.6 lbs). Do USG periodically and amniocentesis
around 16-18wks to rule out any congenital defect.
Control body wt with limited calorie. Consult with your doctor for periodic check up.