cocoa butter does not prevent stretch marks, if your gonna get them, you'll get them, it only helps blisters, itching and dry skin from getting stretch marks.
my sis in law spent all kinds of money on cocoa butter creams, she said these exact words.
its good to still use it though, cuz some pregnant women get bad blisters and it helps prevent that, but as for stretch marks, if you get them, you'll get them.