Unfortunately, stetch marks are mostly genetic. If your mother had then and your grandmothers, chances are you'll be prone to them to.
Nothing can prevent them, but keeping the skin hydrated with something like cocoa butter can help minimize the likelihood and appearance.
In my own case, I found time to be the best way to reduce the appearance of mine as well as getting smaller. The only place I got them was on my breasts once my milk came in, and they were really ugly.
http://www.mayoclinic.com/health/stretch-marks/DS01081/DS...
If you're really concerned about it, talk to a dermatologist to see what they recommend to help minimize the appearance. Otherwise, they're our battlewounds for being brave and giving our bodies to being Moms.