The foramen ovale gradually closes in most infants within the first 3 months of life. The foramen ovale is the natural passageway between the right and left atria in the fetal period and is unclosed. After birth, as the pressure in the body circulation gradually increases and the pressure in the pulmonary circulation gradually decreases, the foramen ovale closes functionally and then anatomically. In some infants, the foramen ovale closes within half a month after birth, in most infants it closes completely within 3 months, and in a quarter of infants it closes completely within 1-1½ years of age. If the foramen ovale is not closed, the child may not show any unusual symptoms, or the foramen ovale may remain open for life, which usually does not affect the child’s health. If the child is found to have an unclosed foramen ovale, a cardiac ultrasound is needed for dynamic observation, and appropriate treatment will be taken according to the overall development.