The human skull is made up of six bones, and the fontanelle is a diamond-shaped bone intersection in the center of the front of the baby’s head, the size of which is indicated by the length of the line connecting the midpoints of the two opposite sides. At birth, the fontanelle is about 1-2 cm, and later increases with the growth of the skull, gradually becoming smaller at about 6 months of age and closing at about 1.5 years of age. The highest part of the fontanelle should not exceed the edge of the bone around it. Therefore, a significant bulge in the fontanelle can generally be determined with the naked eye. Parents should observe the bulging fontanelle to see if it appears suddenly, or they can use their hands to touch the fontanelle area to feel if there is a tightness. Medically, the bulging fontanelle can reflect to some extent the child’s increased intracranial pressure. Therefore, you should also observe your baby’s physical condition for symptoms such as fever, vomiting, convulsions and neck discomfort. If all of these symptoms are present, the baby should be sent to the doctor for examination. The causes of bulging fontanelle are physiological and pathological, as follows: 1. physiological: such as violent crying, exertion, coughing, and fever due to accelerated blood circulation, accelerated heart rate, resulting in increased blood flow, can also appear bulging fontanelle; 2. pathological: mostly seen in meningitis, intracranial tumors, subdural effusion and other intracranial infectious diseases and intracranial occupying lesions when the intracranial pressure is increased (vomiting, vomiting, headache, optic papilledema). Headache, optic papilledema), and hydrocephalus can also cause a bulging fontanelle. If your child has a bulging fontanelle and is in a poor mental state, accompanied by fever and vomiting, it is recommended that you go to the hospital in a timely manner to determine the cause of the bulging fontanelle and then provide targeted treatment.