I never prewash. Never had an issue and I have used everything from Walmart fabrics to LQS fabrics. I was not taught to prewash didn't hear of it til I joined on here. Your out of your comfort zone not prewashing, plagued with the what ifs...we all can relate lol!! If it will bother you and distract you through the whole process just wash them, if it wont bother you while piecing I would just cut and sew. Goal is to have fun and love what your creating...