The foramen ovale is an opening in the atrial septum that is present in all fetuses, allowing oxygen-rich blood from the placenta to pass directly from the right atrium to the left atrium, bypassing the non-functioning fetal lungs. On fetal echocardiography, the foramen ovale is seen as a flap-like structure in the atrial septum, and flow across it can be demonstrated with color Doppler. After birth, when the baby begins breathing and pulmonary blood flow increases, the foramen ovale normally closes. In approximately 25 percent of adults, however, it remains partially open, a condition called patent foramen ovale, which can sometimes be detected on echocardiography and may be associated with certain types of stroke.
Sonography Term