I've used nothing special apart from whatever moisturiser is sitting around, and have no stretch marks - my understanding from the research is that it is a genetic thing predominantly. What you can do though is keep yourself well hydrated (drink water), eat a healthy diet and not gain too much weight too fast, and keep your skin mobile and moist - which means using some sort of moisturiser and making sure you're not just rubbing it in , but moving the skin around as well.

Whatever works for you and makes you feel like you are doing something!