As long as you are quilting fairly closely (lines 4" apart or less), there is no problem. This is because, once the fabrics are quilted, the batting limits how much any one fabric can shrink.
When washed by themselves, fabrics can shrink at drastically different rates. If you are using large pieces of fabric in a quilt and your quilting lines are far apart (say, 10"), then you can run into problems with varying rates of shrinkage.