You won't be able to prevent them completely but you may be able to prolong the time it takes for them to appear. Try rubbing a stretch mark cream like palmers or even vitamin E cream into your belly every day after you have a shower. I used nutrimetics nutri-rich oil and I found that I didn't get stretch marks until the last month. But then again I don't know if that was from using the cream or because my tummy was already stretched a bit from first pg! I think probably a bit of both. Anyway, you have nothing to lose by trying something. Also I found that after pg the stretch marks faded really quickly. Now I have little silver lines on my belly but they are barely noticeable, so it's not so bad.