Preparing fabric for clothing
If you intend to wash your finished garment, you should prewash your fabric(s) before cutting out the pattern. This is especially true if you are sewing with cotton or a washable rayon. Be sure to check the cleaning instructions on the bolt of fabric to be sure a fabric can be washed. If you are not sure, cut a measured piece of the fabric and wash and dry that to assess shrinkage. Otherwise, dry cleaning is an option to washing.