Bio Oil is great! Anything with shea butter in it will keep your skin well hydrated and assist in keeping the stretch marks down. Please try not to let them bother you too much though!
I already have stretch marks on boobs, hips & stomach because I developed really quickly as a teenager. I will be moisturising to try and prevent additional ones from being too bad during this pregnancy, but at the end of the day my current ones really don't bother me - my DH loves my body the way that it is and I feel comfortable in my own skin