Not to burst anybody's bubble or anything, but stretch marks are completely a result of heredity and not affected by lotions or creams. How quickly they fade after childbirth is also just heredity/skin type. Some people get stretch marks during pregnancy, some don't.
I'm not going to knock the lotions, because they definitely help with the itchiness, but don't expect them to prevent or reduce stretch marks. I used Palmer's religiously with my first child, because my belly was so itchy, but I had stretch marks like nobody's business. Fortunately, they faded after the birth. And of course, now they're coming back again. :-)