I was told that if you are going to get them you will get them - theres nothing you can do about it.
But I do think keeping your tummy well moisturised will allow the skin to stretch more -perhaps delay them even.
What you use to keep tummy soft doesnt matter - baby oil is prob the cheapest.
I have none yet and I am 36+3 - been using baby lotion/cocoa butter since around 10wks.