It has to do with more than nutrients.
The umbilical cord is composed of Wharton’s jelly, a gelatinous substance made largely from mucopolysaccharides. It contains one vein, which carries oxygenated, nutrient-rich blood to the foetus, and two arteries that carry deoxygenated, nutrient-depleted blood away. Occasionally, only two vessels (one vein and one artery) are present in the umbilical cord. This is sometimes related to fetal abnormalities, but it may also occur without accompanying problems.
It is unusual for a vein to carry oxygenated blood and for arteries to carry deoxygenated blood (the only other examples being the pulmonary veins and arteries, connecting the lungs to the heart). However, this naming convention reflects the fact that the umbilical vein carries blood towards the fetus’s heart, while the umbilical arteries carry blood away. Source
If this is true, it would seem to make sense that it would be closer to the heart and lungs. But if the nutrients are going into the digestive system, it would make more sense to have it be attached in a more central location to all of these bodily functions. GQ.