Implications of maternal hyperglycemia

Case details
A pregnant mother with a history of long-standing uncontrolled diabetes mellitus has come for a routine check up. The examination reveals a normal pregnancy. Blood chemistry reveals random blood glucose – 165 mg/dl and Glycated hemoglobin (HbA1c) of 10.5 %. What are the possible complications in a fetus under such conditions of maternal hyperglycemia?
A. Fetal hyperglycemia
B. Large fetal size
C. Hypoglycemia after birth
D. Fetal hyperinsulinemia
E. All of the above.
See the image below and try to find out the answer

Maternal hyperglycemia

Figure- Showing the implications of maternal hyperglycemia.

The correct answer – E- all of the above.

The growing fetus of a diabetic mother is exposed to maternal hyperglycemia that leads to-

1) Initial fetal hyperglycemia, a signal for the release of insulin. Constant exposure to maternal hyperglycemia causes hyperplasia of  fetal pancreatic islet cells setting a state of hyperinsulinemia (See figure)

2) Insulin is an anabolic hormone that stimulates biosynthetic processes like endogenous protein synthesis, glycogenesis and lipogenesis. The overall fetal growth is stimulated and that is the reason for,” Large for date” or “Big babies” born to diabetic mothers.

3) After delivery the baby fails to suppress the excessive insulin secretions and develops hypoglycemia.

(Hyperinsulinemia persists whereas there is no more hyperglycemia to balance insulin secretion; hence hypoglycemia gets precipitated if the baby is not fed frequently)

The newborn babies are more susceptible to hypoglycemia, since they have little adipose tissue to provide alternative fuels such as free fatty acids or ketone bodies during the transition from fetal dependency to the free-living state. The enzymes of gluconeogenesis may not be completely functional at this time, and gluconeogenesis is any way dependent on a supply of free fatty acids for energy. Little glycerol, which would normally be released from adipose tissue, is available for gluconeogenesis, but that is not sufficient to fulfill the energy needs. The neonates have inadequate glycogen stores as well, so at the time of need there is diminished outpouring of glucose. The situation worsens further if there is associated prematurity since the glycogen stores are laid in the last months of pregnancy. Hence a premature baby has diminished stores and frequently undergoes hypoglycemia.

4) The hypoglycemia may also be observed during pregnancy, fetal glucose consumption increases and there is a risk of maternal and possibly fetal hypoglycemia, particularly if the mother does not take meals for a longer duration. There is an imbalance between demand and supply of glucose that causes hypoglycemia.

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