Physiological Basis of Nutritional Needs During Pregnancy

The efficiency of placental nutrient transport mechanisms determines fetal health and has important implications for maternal nutrition management. Although the effects on humans are not as detailed as those on animals, a child born to a mother taking high doses of vitamin A has been reported to have urinary system abnormalities similar to those in experimental animals. Excessive vitamin D intake can cause fetal hypercalcemia. While high doses of water-soluble vitamins are non-toxic, physiological competition for transport carriers can become pathological when essential amino acids are forced to compete with excess vitamin C or B, resulting in impaired growth. If maternal hemoglobin levels are reduced due to iron deficiency, the oxygen supply per 100ml of blood is reduced, and the mother must compensate by increasing cardiac output.

During pregnancy, the placenta becomes the main source of progesterone and estrogen, while also synthesizing several hormones that exist only during pregnancy, such as HGG, HPL, HCS, and HCT. These hormones stimulate many processes related to maternal development and have effects on metabolism and nutrition. Other normally present hormones, such as thyroxine and insulin, have altered secretion rates depending on the mother's overall health and nutritional status. During pregnancy, serum nutrient levels are low and the kidneys tend to excrete more nutrients, which creates problems in setting nutritional needs. Additionally, healthy women typically gain about 12 kg during pregnancy. Obesity is not a desirable outcome of pregnancy; being overweight is just as problematic as being underweight.