Modified Pedersen’s Hypothesis
The pathophysiology of macrosomia can be explainedbased on Pedersen’s hypothesis of maternal hyperglycemia leading to fetal hyperinsulinemia and increased utilization
of glucose and, hence, increased fetal adipose tissue. When maternal glycemic control is impaired and the maternal serum glucose level is high, the glucose crosses the placenta. However, the maternal-derived or exogenously administered insulin does not cross the placenta. As a result, in the second trimester, the fetal pancreas, which is now capable of secreting insulin, starts to respond
to hyperglycemia and secrete insulin in an autonomous fashion regardless of glucose stimulation. This combination of hyperinsulinemia (insulin being a major anabolic hormone) and hyperglycemia (glucose being a major anabolic fuel) leads to an increase in the fat and protein stores of the fetus, resulting in macrosomia ( fig. 1 ).