Fetal Blood flow

Blood from the mother and fetus exchange food and oxygen for carbon dioxide and wastes in the placenta. Because a fetus is growing so fast their blood has about 50% more hemoglobin in it to provide much more oxygen to the fetus. Blood flows from the placenta up through the umbilicus and into the fetus. There is about half of it goes to the liver and the other have go into the Ductous Venosus. After a short distance the Ductous Venosus joins the Inferior Vena Cava. Here the blood goes into the Right Atrium and splits again. Some goes into the Right Ventricle and some goes through a hole in the heart called the Foramen Ovale into the Left Atrium. Now most of the blood bypasses the lungs through a vessel called the Ductous Arteriosus which shunts blood from the Pulmonary Trunk into the decending arch of the Aorta. The blood travels down the aorta and splits again. Some goes out to the parts of the body and the rest is taken out to the placenta by the umbilical arteries.


After the baby is born the Ductous Venosus becomes the Ligamentium Venosum which no longer carries blood. The Foramen Ovale will become the Fossa Ovalis which closes the hole in the Right Atrium to the Left Atrium. The Ductous Arteriosus become the Ligamentium arteriosum and the shunt from the pulmonary trunk to aorta is closed. This happens over a short period of time after the baby is born not just as it exits the mother. This link is helpful in explaining what happens. http://www.cayuga-cc.edu/people/web_pages/greer/biol204/heart4/heart4.html