I used this oil through my pregnancy and it helped until the last month when I got a few small strech marks. The downside is that it smells bad and the glass bottle packaging.

I've been using this from the beginning of my pregnancy, twice daily. The smell is rather awful, but it got a bit better as my pregnancy progressed. It is nice and moisturizing, and I can imagine it helping a bit in avoiding stretchmarks (although I don't believe anything REALLY helps in avoiding them...). It sinks in pretty fast as well, but I started using a cream instead of this oil in the morning to avoid stains on my clothes. As I'm only 4 months gone now, I will update regularly.
EDIT: I'm 7 months pregnant now, and still no stretchmarks =D! I do alternate with the Palmers pregnancy oil as that smells a lot better ;).
EDIT: 8 months and still not a single stretch mark =D
Edit: 9 months and no stretch marks... <3
LAST EDIT: I have given birth last week and guess what? Not a single stretchmark =D!!! continued >>