Like so many others I used to pre-wash, but then a lady at a local shop told me she never even washes fabric or battings. She told me in no uncertain terms that fabrics were not the way they used to be (can you tell I'm over 60?) ditto battings.
I took her at her word and measured my next warm and natural before washing and drying.......end result....no shrinkage so this gal has joined the ranks of using a'natural......Fabrics though are another story as my research shows this is a mixed bag as far as what is appropriate. I figure if I'm putting all that work into it, I'm better off safe than sorry! Sign me "Methusola"