The belly button (or umbilicus) is never detached from its fascial blood supply when I perform a tummy tuck (abdominoplasty). Although it appears sometimes to be lower or off to the side before the procedure, that is just merely the stalk and surrounding skin. Once this excess is removed, I place it back anatomically into the midline and a new hole is cut out to inset around the belly button, virtually making it appear without a visible scar.
Classically there are two anatomic landmarks for positioning belly buttons with tummy tucks, one is the midline and the other is a line drawn with the superior iliac crests. The crests are the two bony prominences you can feel on the front of your pelvic bones. This seems straightforward, but actually it is many times not that straightforward as the pelvis can be tilted to one side or the other. In fact pelvic tilt is more common than not. Also many people have lopsided bodies due to one side being wider than another. Just look at your natural belly button and realize it may not be in the exact middle now! So I place the belly button at the level it is currently, ie...I place it where God put it and I try to place it as close to the midline as possible. Fnally I relate all of these facts to my patients to give them realistic expectations, which should be a belly button as close to the middle as possible at or near the level it was before the surgery.