In many ways, a subdural hematoma and a cephalohematoma are similar, which is why people sometimes confuse one for the other. It's important to note the difference, though, because it can have a drastic impact on the seriousness of the injury. On top of that, a subdural hematoma is not as common as a cephalohematoma.
Both injuries are the result of blood pooling to one location on a baby's skull. They can occur when the birth was assisted in some way, such as with a vacuum or forcepts, but they have also been reported in c-sections and unassisted births.
The critical difference is the location of the blood. If it's inside the child's skull, it is a subdural hematoma. If it is on the outside of skull, and therefore more visible to the parents and medical professionals, it's a cephalohematoma.
A cephalohematoma is the less dangerous of the two, despite its more obvious physical appearance. It can make it more likely for the child to get jaundice, however.
A subdural hematoma may be more problematic because the blood is inside the skull, so the brain doesn't have the skull's protection from that pressure. In fact, the condition can be considered life-threatening in some cases.
On the other hand, a cephalohematoma never goes below the skull and pressures the brain, and it generally clears up on its own -- though it may take months to do so.
Birth injuries, even minor ones, can be very worrisome to new parents. Serious injuries can be life-changing, for both the child and the parents. If your child was injured, you need to know if you have a right to compensation.
Source: Parents, "Cephalohematoma," Alan Greene, accessed Jan. 13, 2017