How soon after birth does the foramen ovale close?

E. The foramen ovale functionally closes almost immediately after birth as pressure in the right atrium decreases and pressure in the left atrium increases, thereby pushing the sep-tum primum against the septum secundum. Anatomical fusion occurs much later in life; more than 25% of the population has probe patency of the foramen ovale, in which anatomical fusion does not occur.