What is a birth trauma?

http://www.birthtraumaassociation.org.uk/what_is_trauma.htm

I found this article to be very interesting for me. I too had a very traumatic birth and when I got home from the hospital and could not sleep I often asked myself, “why?” I would start to fall asleep and awaken shaking, having a panic attack, and thinking that I was surely going to die. The first few times this happened I often asked myself if this was related to how I had given birth and maybe I was scared to fall asleep as this was in the back of my mind. I think for myself the trauma of the birth really did have an effect on me and my postpartum depression. I would love to hear any comments from the readers as to your experiences.