I chose not to have the injection.
I wanted a natural drug free labour & that is what I had.
When my daughter was born I put her straight onto the boob & then got straight out of the pool (waterbirth) & TMI!!! as I stood up my placenta just fell out LOL.
So even without the injection it only took about 2-5mins to come. No complaints from me coz that was the easy part LOL!
I also had no stitches.
Personally though I think you just have to keep an open mind. Plan to not have the injection but be ok about having it if you need to.?.?