Fetal nutrition
1994
Aldoretta, P.W. | Hay, W.W.
A review of fetal nutrition is presented, emphasizing recent developments. A brief introduction to basic methodology used in fetal metabolic research is provided. Nutritional requirements for fetal growth are discussed in terms of body composition and caloric content of fetal tissues. This is followed by a discussion of nutritional requirements for ongoing energy needs of the growing fetus; use of both the Bohr principle and the Fick principle to measure oxygen consumption is reviewed. Fetal weight-specific metabolic rate is higher in early than in late gestation and in human fetuses is greater than that in infants and children, reflecting the more rapid rates of nutrient substrate processing and body growth. Carbohydrates, amino acids, and lipids are then individually reviewed. Placental transport, and fetal utilization for oxidation and carcass accretion are discussed for each major nutrient substrate. Glucose is the principle energy substrate but its contribution to fetal energy production includes lactate that is produced in the placenta and transferred into the fetus. Lipids account largely for fat accretion in the third trimester. Amino acids are the major source of carbon and nitrogen for fetal protein synthesis; the placenta acts to produce a unique supply (quality) as well as total amount (quantity) of amino acids for fetal metabolism and protein accretion. Lastly, a brief discussion of fasting as a model of maternal and fetal malnutrition is presented. The principle adaptation of the fetus to nutrient deprivation is short-term substitution of fetal body stores (glycogen, protein) for energy production, whereas long-term nutrient deprivation leads to a reduction in the rate of fetal growth.
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