Originally Posted by MTS

STEP AWAY FROM THE MACHINE.

PUT THE QUILT DOWN.

Do not wash a quilt top before it's quilted.

It's not that it will all fall apart, but it will be a mess to iron again, as the seam allowances are all over the place, and frayed.

The fact that you think some fabrics might shrink at a different
rate than others won't be solved. They'll shrink, but wouldn't be stabilized by anything.

Actually, you'll have more control over the shrinking if it's washed after it's quilted.