Babies have a small pit on the top of the head, the vast majority of the normal phenomenon, because before the age of one and a half years old babies are born after the fontanel, fontanel is mainly the two sides of the skull is not yet fully closed a manifestation of the body continues to develop, especially in the age of one and a half years old, the basic fontanel can close. This is a relatively normal situation, you can usually see the fluctuation, with the heartbeat continues to rise and fall, if the pressure may have the feeling of cystic fluctuation, these are normal phenomena. Of course, there is also the posterior fontanel, which closes around the age of half a year and is usually not palpable. However, there are other abnormalities, such as hydrocephalus in infants, which can manifest itself as an outward bulging sensation and requires appropriate treatment, and the child may exhibit certain abnormalities. If the swelling does not heal after one and a half years of age, it is necessary to go to the hospital to see if it is a developmental abnormality or other conditions.