Stretch marks or striae gravidarumare (associated with pregnancy) as a dermatologist may refer to them as is the result of damaged elastin skin fibers.
Elastin is the protein in the skin which gives it flexibility and allows it to stretch and subsequently recoil back to it's original position.
Elastin makes up approximately 4% of skin tissue. When the elastin fibers are damaged, they appear as stretch marks. It is important to mention that stretch marked skin is still healthy, it has just changed in appearance visually and textually. Stretch marks can be the result of pregnancy, obesity, growth spurts and rapid muscle growth.
So the bad news first... no treatment can 'cure' stretch marks once they have formed. (It may be possible to minimize the appearance by applying topical remedies and having procedures such as laser resurfacing techniques, tummy tucks and dermabrasion.)
The good news that may come to late is that prevention to a certain extent may be possible. During pregnancy or intense bodybuilding, one can apply a topical ointment that will reduce inflammation and moisturize the compromised elastin tissue.
Ingredients that have shown to be helpful include essential fatty acids, alpha lipoic acid or r-lipoic acid, lavender essential oil, rosemary essential oil, gotu cola extract, vitamin A, vitamin E, vitamin C and hyaluronic acid (use the plant source). Another key is to avoid dehydration, make sure you are drinking enough good clean water every day.