When the skin gets stretched by pregnancy, weight gain, or the normal growth of the teen years, depressed lines can develop. These stretch marks are a type of scar, which is usually red or purple to start, then fades to a glossy white. They're most common on the belly, thighs, hips, breasts, and lower back. Chemical peels or laser surgery can reduce them. Unfortunately, lotions and creams usually don’t do much.