because I had the birth erbs in the 50s I should just speak of the affect in sleeping I never sleep with my parents but I think it a great Idea with a baby with erbs to have there parents close for sleeping 
The why is because I know the Fact that when you are injured with birth erbs . You are born in to Pain 
but true 
The best thing is to be there for them in sleep you bet they turn more to find a position ware it hurts less still do it at 61, I think The mattress on the floor is a good idea for possible falls 
I should add that the side affect of birth erbs pain is that over a life time it gives you a high tolerance of pain it self
it also helps in trying and dealing with the pain level in trying. That is another true but strange thing with these injuries,I think base on my experience best wishes,
Tom
