Caput succedaneum: This is a common condition in newborns, especially after vaginal delivery. It is characterized by a soft, puffy swelling on the scalp, often on the back of the head, due to fluid accumulation. The condition is usually harmless and resolves on its own within a few days.

Cephalohematoma: A collection of blood between the skull and its covering, often resulting from birth trauma. It appears as a well-defined bump on the scalp and can take weeks to resolve. Unlike caput succedaneum, cephalohematoma does not cross suture lines.
Subgaleal hemorrhage: Although less common, this condition involves bleeding into the space between the skull and the scalp. It can be more extensive and may cross suture lines, potentially leading to significant blood loss.

Skull fracture: A break in one or more of the bones of the skull, which can occur due to birth trauma. While less common, it is crucial to identify and manage appropriately to prevent complications.
Intracranial hemorrhage: Bleeding within the brain or between the brain and the skull. This is a serious condition that requires immediate medical attention to prevent long-term neurological damage or death.

Dermoid cyst: A rare congenital condition where a cyst forms on the scalp, containing skin and sometimes hair. It is usually present at birth and may appear as a bump.
Encephalocele: A rare neural tube defect where a portion of the brain and its covering membranes protrude through an opening in the skull. It can present as a bump or sac on the back of the head.
Lipoma or other soft tissue tumors: Although extremely rare in newborns, these could potentially present as a bump on the back of the head.