Fig. 1. Results of maternal hyperglycemia modified according to
Pedersen�s hypothesis.
Modified Pedersen�s Hypothesis
The pathophysiology of macrosomia can be explained
based 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 ).