Well...I havent had my baby yet, but I do know plenty of people (and younger girls) who have had there's and the doc says not to work out or exercise until about 6 weeks after the baby is born. Or whenever your doc/midwife says you can. Cause your inside of your body is still very sensitive and has gone through alot while being pregnant and if you do strenuous workout (lifitng weights, sit ups...) it can damage and cause internal bleeding. And no...I am not lying, so people dont come and tell me that i am! he stretch marks do lighten after a while, but not right away. I do not think that there is anything you can do about them, they are permanent damage to the skin and will lighten up when they get 'older'.