I have had a little previous experience with this. In that experience of being treated for both conditions previously mentioned with multiple natural and medicinal remedies, it did not clear up, and the baby was fine. My midwives told me that this is very normal and I was lucky I had not experienced this unpleasantness before, and sometimes the pH on a pregnant woman is just funny like that, and will probably clear up on its own after pregnancy.
I was more concerned about it than they were. I had read that BV in particular was dangerous, and read lots of yeast horror stories as well. I was scared of passing things to the baby, getting things in my blood stream, etc. Nothing we were using worked! But they seemed confident that all was well, though, even though I thought it was very odd and felt pretty concerned. It was just a really yucky situation to be in, especially for someone who'd never experienced this before at all. I am of the belief that they must have been right, unless someone else here feels that was horrible advice on their parts.
If it'll make you feel any better, get it checked out, but there are no guarantees that anything will definitely "cure" it regardless, and in the end your caretakers (depending on who they are and what their philosophies are) could more or less throw their hands up and say not to worry about it and just deal with it. Or maybe you'll get lucky and they'll admit you to a hospital (j/k!!!).
One thing that occurs to me now and then when I think of these conditions and the paranoia surrounding them is that I learned that many women have BV or yeast overgrowth but don't even know it. Sometimes symptoms are so mild that it's not even recognized, and those women and their babies end up just fine. Anyway, I never went into preterm labor. Not to say it doesn't happen, I'm just saying.