The reason why skin and fat hang off and tummy muscles remain stretched and flabby after weight loss is because the muscles remains where it was left and the skin is damaged and does NOT shrink to fit the new, smaller body scaffold and frame.
In any body contouring surgery such as a tummy tuck, the abdominal wall is literally reconstructed and "taken-in" layer after layer. First, the loose, sideways located muscles are put back together. The extent to which this is done - determines the flatness of the tummy and waist narrowing. Once this is done, the abdominal skin and fat are pulled down and excess skin and fat are removed. Liposuction of the back and hips may be done to further improve buttock and hip definition. Upon completion, you could pretty much be flatter than you ever were and have a very nice figure.
At this point, if you became pregnant or massively obese again - the intra-abdominal stretching would disrupt and stretch out the muscle repair and again re-stretch the skin. But - trying to repair things later would be much more challenging than the first time around because of the scarring,
It is BEST to have this operation after ALL tummy stretching is done - after you lost your weight permanently and completed your family.
Dr. P. Aldea