Glucose represents the main source of energy for the fetus, accounting for 90%. To prevent the conversion of the body’s own proteins into carbohydrates and to provide optimal nutrition for the unborn child, 320-380 grams of carbohydrates are thus required daily for a requirement of 2,600 calories. The fetus itself needs 30-50 grams of glucose a day in the last weeks of pregnancy. Of the carbohydrates in the mother’s blood, about 40% are needed by the placenta, which is also capable of glycogen synthesis as well as storage.
Carbohydrate metabolism in pregnant women is influenced by hormones of the placenta (placenta), such as human placental lactogen (HPL) and by placental steroid hormones. As the functions of all endocrine organs are increased in early pregnancy, there is an increase in the performance of the islet cell organ as well as the insulin-producing beta cells in the pancreas, resulting in increased insulin serum levels (hyperinsulinism).
Hunger states, such as forgoing breakfast, are less well tolerated during pregnancy and cause significant metabolic changes. Because of this, pregnant women often have elevated insulin levels, low blood glucose levels (hypoglycemia), and increased ketone bodies in the plasma (ketosis) due to increased fat breakdown. These symptoms are exacerbated during starvation states. To counteract hypoglycemic reactions (hypoglycemia), care must be taken to ensure adequate carbohydrate intake during pregnancy. The fetus is not negatively affected by the short-term hypoglycemia, ketosis as well as the hyperinsulinism of the mother, since the latter has developed sufficient glycogen stores of its own in the liver. With increasing duration of pregnancy (gestational age), the mother’s glucose tolerance decreases, resulting in a reduced effect or a more rapid degradation of insulin. The changes in the mother’s blood glucose levels also lead, with a slight delay, to changes in the fetal blood glucose level (blood glucose of the child), which is about 25-30% lower than that of the mother. The difference in blood glucose levels can be explained by the placenta‘s own consumption of glucose. With increasing gestational age, the glycogen content of the placenta decreases. In contrast, the glycogen content of the fetal liver increases. If the mother is in a state of starvation, glycogen is broken down in the liver of the fetus. If, on the other hand, the pregnant woman has high blood glucose levels (hyperglycemia), for example, due to a deficiency of magnesium, potassium, pyridoxine and chromium, increased glycogen formation occurs in the fetal liver. This explains that when the mother has prolonged insulin-induced low blood glucose levels, normal blood glucose levels are measured in the unborn child.
