Placenta is an organ to which the fetus is attached by means of an umbilical cord. It is the life line of fetus. it is an oval spongy structure, 6to 7 inches in diameter and weighs nearly 450 grams. It is however, expelled after childbirth. The nutrients, electrolytes,water and oxygen are transferred to the fetus for its nourishment and the fetal excretory products are transferred to the maternal blood. The placenta maintains two completely separate blood supplies- the maternal circulation that remains in the intervillous space and the fetal capillaries separated from the maternal blood by two layers of cells. Placenta therefore functions as a regulator for transfer of nutrients to the fetus.
- Nutrients such as folates, iron, vitamin C are allowed to pass to the fetus in sufficient amounts through the placenta even at the cost of maternal reserves.
- However, in case of nutrients such as thiamine, riboflavin, vitamin B12, pyridoxine and vitamin D, the placenta allows the transfer according to the needs of the mother and the fetus.
- The fat soluble vitamins A and E are present in lower amounts in fetal than in maternal blood.
Undernourishment of the mother leads to smaller size of placenta and thus fewer cells are available to transfer of nutrients, oxygen, etc. to fetus, leading to low birth weight.