The foramen ovale is a structure that exists during the growth and development of the heart and is a small hole in the right and left septum. It is normal for the foramen ovale to open during pregnancy. If the foramen ovale closes during pregnancy, it is called premature closure of the foramen ovale, which instead has an effect on fetal heart development. In newborns, the foramen ovale can remain open up to three years of age and should normally close around three years of age. After three years of age, the foramen ovale still remains open. In this case, heart function should be evaluated according to the cardiac ultrasound, and if it does not affect the heart function, it can be observed temporarily without treatment. If it affects the blood supply to the heart, minimally invasive treatment can be taken to seal the foramen ovale.