What is a defining feature of cephalhematoma in newborns?

A defining feature of cephalhematoma in newborns is that it is a collection of blood between the periosteum and the skull bone. This condition occurs due to the rupture of blood vessels during labor and delivery, often as a result of the pressure exerted on the infant's head during passage through the birth canal. The blood accumulation is localized and does not cross suture lines, which is a distinctive characteristic that helps differentiate it from other conditions such as caput succedaneum.

In cephalhematoma, the blood forms a well-defined mass that can usually be felt as a soft swelling at the site of the collection. This specific location of blood collection is crucial for diagnosis, as it indicates that the bleeding is confined beneath the periosteum, thereby allowing the bony skull to remain intact apart from the blood accumulation.

The other options highlight factors that do not accurately describe the nature of cephalhematoma, such as the ability to cross suture lines, which it does not, and emphasizing swelling without specifying the underlying pathological process. Additionally, while it may result from a birth injury, not all cephalhematomas are necessarily associated with trauma, as they can also develop from the inherent stiffness of the fetal neck or