I have this happen all the time. Usually prewashing helps. I can see shrinkage when pressing. I steam press, don't like dry pressing not definite enough. When everything on a project shrinks it seems to work out. If not I'm good at creative add ons.
I have a major problem now. I bought fabric from LQS for a class cut there. Was so excited about project that I proceeded to cut 12 background sq 12 x12. After I got home I had to wash because of allergies. Sq have shrunk to 11.25". I will take it to class next week and see what instructor (store owner ) says.