And this allows the oxygen rich blood to bypass those nonfunctional lungs within that developing fetus. Now, normally at birth, this valve shuts close. But in some fetuses, the foramen ovaly fails to close properly, which leads to a permanent valve system that connects the two atrium of the heart. And this condition is known as the patent for Raymond, or valley, and it is the most common type of atrial septal defect. Now, what exactly is an atrial septal defect? Well, septal simply means wall.