The modified Pedersen’s hypothesis explaining the pathophysiology of macrosomia. When maternal glycemic control is impaired and the maternal serum glucose level is high, glucose crosses the placenta – but insulin does not. In the second trimester, the fetal pancreas responds to hyperglycemia and secretes insulin in an autonomous manner (hyperinsulinemia). The combination of hyperinsulinemia and hyperglycemia leads to an increase in protein and fat stores in the fetus, resulting in macrosomia.