Why the blood of the mother is separated from the blood of the fetus?

The blood of the mother is separated from the blood of the fetus primarily to prevent the immune system of the mother from attacking the fetus, which is genetically distinct. This separation occurs in the placenta, where nutrients and oxygen are exchanged without direct mixing of maternal and fetal blood. Additionally, this separation helps maintain different blood pressures and chemical environments necessary for the development of the fetus.