where does blood come from before it enters the left atrium
Fetal Circulation The red blood that enters the fetus passes through the fetal liver and enters the right side of the heart. The red blood goes through one of the two extra connections in the fetal heart that will close after the baby is born. The hole between the top two heart chambers (right and left atrium) is called a patent foramen ovale (PFO). This hole allows the reddest blood to go from the right atrium to left atrium and then to the left ventricle and out the aorta. As a result the blood with the most oxygen gets to the brain. Blood coming back from the fetusâs body also enters the right atrium, but the fetus is able to send this blue blood from the right atrium to the right ventricle (the chamber that normally pumps blood to the lungs).