The ductus arteriosus allows fetal blood to move from the pulmonary trunk into the aorta. The ductus venosus on the other hand is a fetal vessel that transports blood from the umbilical vein to the inferior venacava. Ductus arteriosus is a blood vessel connecting the main pulmonary artery to the proximal descending aorta. It allows most of the blood from the right ventricle to bypass the fetus's fluid-filled non-functioning lungs.