Is it normal for the skin to shrink between the bottom hole and the top hole of a navel piercing?

well that depends... when you first pierce it your navel will swell so after some time it may seem like the skin is shrinking but the swelling is just going down.thats what heppend with mine but if u feel that this is still odd u should go see your doctor about it. ... It does happen, just like with surface piercings, the piercist will warn you that over time the skin will shrink. its nothing serious though.