Why do people have birthmarks?

According to sylvia browne that they are wounds from battles from past lives.

Birthmarks are on your body when you are born. That is why they are called birthmarks. They appear in many colors. Doctors do not know what causes them, and no one has discovered a way to prevent them from appearing. Some people don't have any. Others have many. Most birthmarks are fine and many parents have them checked on their children, if you wish a doctor can check them out to make sure it is okay.