Don't scratch if your itchy, drink lots of water, and keep your skin moisturized.
My mum said to just keep the skin hydrated. Drink lots & Moisturise every day especially in those stretch mark prone areas. Worked for her so fingers crossed it does for me too! :)
I use penzim gel (made out of enzim, to fix scars) but I once read that stretch marks come from inside and out, because of hormones and the best way to provent them is to keep the body hydrated... I don't know if it's true or not, but I am going to drink a lot of water this pregnancy just in case if it's true :')