I pre shrink my 80% cotton 20% poly batting, but that is a matter of choice. If you don't pre shrink your cotton batting your quilt will "crinkle" the first time you wash. This is what some quilters want and some don't. I pre wash all my fabrics so I shrink the batting too. Quilts made from repoduction fabrics look old when you don't pre shrink fabric or batting. If the batting is in a package it would be good to allow it to relax before using.