There have been what seem like a gazillion threads about "washing or not washing fabrics"
Check it out for yourself.
Measure some fabrics BOTH lengthwise and crosswise. Wash and dry it. Measure it again.
In my experience, most woven cottons shrink some - some a little - some a lot - and even "quilt shop quality fabrics" have shrunk for me. A Michael Miller black shrank more than two inches in width.
I have quite a few 35 inch lengths that were "quilt shop quality" - that I know I purchased at least a yard of - and that was when I was using the warm wash - which is tepid - and the cold rinse.
Cold water washing may minimize shrinkage.
I actually like some fabrics better after they've been shrunk (tightened up).