I was under the impression that Bio Oil only helped fade existing stretch marks, not prevent them from appearing.

I agree with Cherry that if you're going to get them, you're going to get them. I was lucky and only got one small one with my DD. I was surprised because I actually already had some on my hips and breasts from puberty so thought I'd get them for sure.

I've used Bio Oil on my lap scars to help fade them and it's done nothing. I personally wouldn't bother.