Fetuses need oxygen because (like us) they are made up of cells that use aerobic metabolism. Aerobic metabolism is a system used by cells to make cellular energy out of glucose (sugar) and Oxygen. Fetuses, which start out as one unique cell, need oxygen because they have the same machinery.
If for some reason they didn't get enough oxygen they (like us) would start producing acid and 1/16th of the energy they were producing before and the cells would die.
Umbilical cord
The mother's blood supply enters the foetus via the umbillical cord and allows oxygen to diffuse from the mother's blood into the foetus.
The umbilical cord takes nutrients and oxygen to the fetus.
Through the umbilical cord from the placenta since a fetus can't use lungs to obtain oxygen. Read more in the link below about fetal circulation.
The umbilical cord delivers oxygen and nutrients to the fetus and removes wastes.
The fetus receives oxygen from the mother through the placenta. The mother's blood, high in oxygen, passes through the placenta where it comes into close contact with the fetus's blood, allowing for the exchange of oxygen and carbon dioxide. This process ensures that the fetus receives the necessary oxygen for development.
First of all, the human fetus does have oxygen. The oxygen is obtained from the mother's blood via the placenta. But if the fetus did not have oxygen temporarily, s/he could still metabolize glucose. This would be done the same way that other humans metabolize glucose without oxygen--by converting it to lactic acid.
The umbilical cord supplies the fetus' oxygen.
The fetus gets oxygen and nutrients from the mother's bloodstream through the placenta, a temporary organ that connects mother and fetus. Waste products produced by the fetus, such as carbon dioxide, are passed back through the placenta into the mother's bloodstream for her body to eliminate.
Our body obtain oxygen to our body by breathing.
The purpose of the umbilical cord in the development of a fetus is to provide nutrients and oxygen from the mother to the fetus, as well as to remove waste products from the fetus.
Oxygen deprivation of a fetus is called fetal hypoxia. It occurs when the fetus does not receive enough oxygen during pregnancy and can lead to serious health complications for the baby. Immediate medical intervention may be necessary to prevent long-term consequences.