most likley they will just arrive one day when you wake up with no warning i remember getting 1 or 2 on each side when i was around 20 weeks which faded in the space of a few days as i put tons on vitamin e cream on which i think helped them fade quickly - i then didnt get any more stretch marks untill about 3-4 weeks ago, i havent really botherd putting cream on every day, just when i remember and they are starting to fade they are silver in colour when they first appeared they were red
if you get them you get them if you dont then you dont but you will most likley get them if it is in your genes, i dont think creams prevent you getting stretch marks but i think it helps with making them less itchy and making them fade a bit quicker