3 year old baby head with bone bulge is generally abnormal, may be head trauma, calcium deficiency, intracranial tumors and other reasons. 1. Head trauma: 3-year-old babies are more playful, the amount of activity is relatively large, play in the process of accidentally bump or fall, hit the top of the head caused by subcutaneous hematoma, the top of the head will have a bone bulge phenomenon, the hand may have a fluctuating sense of local pressure, the skin around the blue-purple color, it is not normal performance. 2. Calcium deficiency: 3-year-old baby’s body lacks a lot of vitamin D and calcium, the bones of the skull have certain changes, manifested as saddle-shaped skull, the skull will be deformed as a saddle-shaped center has a concave groove on both sides of the more pointed, this situation is also not normal. 3. Intracranial tumors: 3-year-old babies have osteoma, hemangioma and a series of tumor diseases, will also have a bone bulge in the top of the head performance, this is not normal. There are more reasons for 3-year-old babies to have bone bumps on the top of the head, and it is recommended to consult a doctor in time for examination.