I've been diagnosed with it as it was picked up with a swab test for thrush, and I'm currently doing a lot of reading around it.
The thing is, 25-30% of women carry group b strep at any given time, but the infection does come and go. They're trialling a quick test in labour internationally which is the most sensible choice I think, because as it stands you're given the antibiotics if you test positive at any point in pregnancy and that both misses a lot of women who would be positive in labour and catches a lot who are negative.
Tests have shown babies still show negative overgrown of bacteria in their gut a year after their mother takes the antibiotics in labour. Obviously not a big thing compared to a serious infection, but of women with group b strep, only 3-4% will pass it on in labour with no antibiotics, and of the babies who contract it from within that 3-4%, 1-2% will have an infection so severe it may be fatal (usually when they haven't had antibiotics) but it most cases there are other issues- e.g. Baby premature, other risk factors.
There are also studies suggesting if mothers take probiotics in the last month of pregnancy there's a 40% chance they won't have the infection even if they tested positive at the start.
So choosing the certainty of giving a high percentage of babies antibiotics they may not need vs other ways to target it makes little sense. There's a really good website, evidence based birth, with lots of info on the studies into this. I think the NHS should switch to the rapid test in labour model, but I'm not convinced that the approach used in the states of testing everyone earlier in pregnancy is that much better given how many unnecessary antibiotics are given out. I'm going to ask for a retest closer to delivery and take probiotics, but since I won't be able to have a test in labour I will take the antibiotics regardless and just try really hard to breastfeed and maybe give infant probiotics to offset the damage to baby's gut. At a minimum, I want to make sure I do everything I can to avoid her having to be tested/have antibiotics herself, and even though the risk of GBS is v low it's also v serious so that's the priority.
I'm also a bit concerned about timings and making sure I get four hours antibiotics but I guess that depends a lot on the hospital, and I'm hopeful mine will be ok about admitting me to get it started even though I'd obviously rather labour at home for longer. There isn't enough clear info about this out there, but I think the call to test all women should really be amended to testing women in labour (apparently the test can come back in thirty minutes) as otherwise it just seems it will result in higher numbers getting unnecessary antibiotics without fully reducing the risk of missing other women.