I was actually just looking into this. This time around I'm going to squat. It helps the baby to come out with ease. Laying on your back is counter productive to labor.
I was on my back with my first and on hands and knees with my second. Second labor was much easier! I did not tear at all with my second even though I had a 4th degree episiotomy with my first. Back position is the worst!
With my first and second I was on my back and teared a little and did stitched me up. The third I was on my side and didn't tear... This is my third and I'm a little nervous of how I might be positioned...
I was on my back with my first. They wouldn't allow me to do anything different. But I watched a bunch of birth videos and and women have done them squating which aides in the baby passing through the birth canal. Less tearing.
With my first I had to use something like a monkey bar. #2&3 I was on my side with knee under me and my husband holding my other foot-zero tearing or stitches. #4 I went old school on my back