I don't pre wash them but I do heavy starch and hot press all my fabric before cutting regardless of what brand it is. I figure if the fabric will bleed or shrink it will do it wet with starch and a hot iron. If you are sensitive to fumes some fabric may have a sizing on them that could irritate. I always wash the quilt when it's finished. I have lots of CT fabrics and mix them with other brands in a quilt and never had a problem so far.