What happens to the foramen ovale after birth?

After birth, the foramen ovale, which is a small opening between the right and left atria of the heart in a fetus, typically closes. This closure occurs as the pressure in the left atrium increases due to the influx of blood from the lungs, while the pressure in the right atrium decreases because the umbilical circulation is no longer present. When the foramen ovale closes, it effectively becomes the fossa ovalis, a small depression in the atrial septum. This transition is a normal part of the circulatory changes that occur when a newborn begins to breathe air and the lungs take over the oxygenation of blood.

The other options do not accurately reflect the physiological changes that occur after birth. The foramen ovale does not expand significantly; rather, it functions primarily to bypass the non-aerated lungs during fetal life. It also does not become the aorta, as the aorta is a distinct blood vessel responsible for distributing oxygenated blood from the heart to the rest of the body. Lastly, while in some rare cases the foramen ovale may remain patent (open), in the majority of infants, it closes shortly after birth.