I never really understood the approach to testing either.
I have tested positive for Strep B, but this information came out of tests unrelated to pregnancy.
Because I had Strep B, along with a couple of other factors (large baby, notch on one of the arteries in the womb), I was considered high risk. This meant I couldn't have a water birth in the nice mother & baby centred bit of the hospital (I forget now what it's called) that I would have preferred and had to have the more medical approach instead. In practice this meant I had have continuous monitoring and the midwife strongly encouraged me to stay on my back (which was not what I wanted to do) although it's my understanding that a more enlightened midwife could have monitored us fine without subjecting us to this.
I'm really not sure if Strep B alone makes your birth high risk though.
Although lots of people do have Strep B, and they take it very seriously if you do have it, it seemed to me that my health authority didn't test for it as a matter of routine, which didn't any make sense to me!
It's worth bearing in mind however that even if you do have Strep B, the chances of it adversely affecting your baby are very small indeed.
The main lesson I learnt from this is that if I do give birth again. I will make sure I discuss with the midwife how she is going to deal with the monitoring, and if her approach is to insist I'm on my back for the labour, I will insist on asking for another MW. This will be the most important (possible the only!) thing on my birth plan.
I would advise speaking to your midwife about this. At our hospital, we could ring up the midwife team with any questions - can you do this? (Might be worth just ringing the hospital and asking if it's possible to speak to the MW team).
I hope that's helped - and not worried you too much!I hope someone can answer your question soon.