The majority of babies have a small pit on the top of their head, which is normal, because before one and a half years old babies will have fontanel after birth, fontanel is mainly a manifestation of both sides of the skull not yet completely closed, with the continuous development of the body, especially at one and a half years old when the basic fontanel can be closed. This is a relatively normal situation, usually you can see fluctuations, with the heartbeat constantly undulating, if pressed there may be a feeling of saccadic fluctuations, these are normal phenomena. Of course, there is also posterior fontanelle, which closes at about half a year of age and is usually not palpable. However, there are other abnormalities, such as hydrocephalus, which can feel like an outward bulge and require appropriate treatment, and the child may show certain abnormalities. If it does not heal after more than one and a half years, it is necessary to go to the hospital to check whether it is a developmental abnormality or other conditions.