Stretch marks are scars in the skin. Like scars, they never fully go away. There is also nothing you can do to prevent them if you are prone to getting them. They are hereditary.
Keep your skin moisterized, although it won't stop them, it doesn't hurt
After time, your stretch marks will fade, but will never permanently be gone. Depending on the severity, they will range in color. At first they'll be purple, later they'll fade more towards skin color but may always have a silvery-shiny tone to them. They are also indented, so if you run your finger over the stretch marked skin, it will feel bumpy.
Welcome to motherhood! Hope you enjoy your stay