A bulge at the back of the baby’s head may be caused by sebaceous cysts, cavernous hemangiomas, trauma and other reasons, generally surgical treatment, can be timely medical care. 1. Sebaceous cysts: occurring in the head, face and back, manifested as a prominent skin surface of the mass, and the skin is closely linked to the main surgical removal of the main. 2. Cavernous hemangioma: it is a kind of hemangioma that appears after birth, if there is no bleeding tendency and the enlargement is not obvious, it can be observed and followed up, and be treated by surgery if necessary. 3. Trauma: when the baby is traumatized, there will be a bulge at the back of the head. It is recommended to consult a surgeon for a complete CT scan of the head and other relevant examinations, and the surgeon will evaluate the treatment method. There are also other possibilities such as cranial hematoma and choroidal tumor, so it is recommended to consult a doctor in time for a clear diagnosis and active treatment.