As the diaphragm of infants (located on the medial side of the penultimate intercostal space of the thorax) is relatively stiff, costal edge eversion (like trumpet flower phenomenon) will occur to varying degrees. For relatively fat infants, costal edge eversion is not obvious; For relatively thin infants, costal eversion is more significant, and some asymmetry will be found on both sides. This phenomenon has nothing to do with calcium deficiency and will gradually ease at the age of 2-3.