batting packaging have instructions for pre-shrinking your batting if you feel you need to...it also tells you how much it will shrink. everyone really needs to get in the habit of reading their packaging it contains a wealth of valuable information.
looser weave fabrics shrink more than tight weave fabrics...so homespuns will shrink ALOT compared to moda cottons, which will shrink more than batiks.
if shrinkage is a concern you should always pre-wash your fabrics. i have never pre-washed my batting, i just make sure i purchase the batting that is going to behave the way i want it to...such as only shrinking an inch or two...