The best advise is not to get belly piercing since is an area of high bacterial content, they get infected, scarred, and when you become pregnant, like you did, it stretches and does not recoil. Your options are limited. Either have the skin excised and you will substitute a scar for a scar. Or have a tightening procedure done. Tightening can be accomplish with Radiofrequency, infrared or fractional ablative lasers.