I have done a total turn around about pre washing. When I first started quilting many years ago - I did pre wash everything, mostly to set the colors and just in case they did shrink. Then as the fabrics improved and the dyes became better - I stopped. I did a stack n wack and they said not to pre wash. It was fine - so I stopped washing.
After having an issue with a backing fabric really shrinking and reading about the chemicals used in fabric dyeing, especially batiks - I am back to pre washing, especially when I am working with kids.
Jane