Fig. 3
From: Bergmann’s rule is a “just-so” story of human body size
Human fetal circulation. The relative amount of oxygen in the fetal blood is greatest in the upper thorax, neck, and head, indicated by the red color of the vessels ascending from the heart. Blood flowing to the abdomen and legs is less well oxygenated, indicated by the violet color of the vessels descending from the heart. Vessels colored in blue indicate deoxygenated blood returning to the heart via the umbilical arteries (adapted from https://www.anatomynote.com/human-anatomy/infant-child-anatomy/fetal-newborn-baby-blood-vessels-circulation-diagram/)