Stretch Marks can be prevented?

I believe many women, including me is worry about getting stretch marks. Can it actually be prevented? I found myself scratching my stomach at times because it's itchy, and I heard that this is because the stomach is stretching, and we could avoid stretch marks by keeping our stomach moisturised. I'm using Bio oil at the moment, and heard some friends are using cocoa butter. What's better? We could get it cheaper online than the retail pharmacy (even with the postage), I get my elevit & Bio oil through Pharmacy Direct now. I guess as long as it's a good moisturiser, safe, and make sure it's not some herbs & essential oil that cannot be used during pregnancy, which induce contraction.

Oils to avoid during pregnancy:

Anise
Bay
Basil
Camphor
Caraway
Carrot
Cedarwood
Cinnamon
Clary Sage
Clove
Comfrey
Cypress
Fennel
Hyssop
Jasmine
Juniper
Marjoram
Mugwort
Myrrh
Nutmeg
Oregano
Pennyroyal Peppermint
Rosemary
Sage
Sassafras
Tansy
Thuja
Thyme
Wintergreen
Wormwood
Yarrow

Oils to avoid in first trimester: Chamomile, Frankincense, Geranium, Melissa, Rose
Source: http://www.earthyfamily.com/arom-caution.htm

Also:
Herbs to Avoid during pregnancy



Also, keep the weight gain steady, about 1/2 a kilo every week from the 4th month to the 8th month, the recommendation is to aim at gaining 11-15 kilos throughout the whole pregnancy.

Really good book that answers all my questions: