Wanna hear something funny? I had my baby today! Online relaxing for a few min tonight after the whirlwind of labr, delivery , guests etc. Anyway I was GBS pos & meant to come in at 6-8 minutes but short labor & lots of am traffic meant I didn't get to the hospital until it was too late for antibiotics. They took my new baby up for bloodwork, no other consequences. It is too early for results, but thankfully no one seems worried. Baby is well and beautiful. So based on my experience I'd say try to get there early but don't panic of you can't.
just because you test positive at 36 weeks, doesn't mean you will be when you go into labor.
just because they pump you full of antibiotics, doesn't mean that the baby benefits from it- especially if you have quick labors. you are supposed to have 2 doses that are finished an hour before delivery. not sure about you, but that's not happening over here.
in some hospitals, if you are allergic to penicillin (like yours truly), they don't consider you treated, even if you did get the full regimen & your baby gets subjected to all kinds of testing, possibly for no reason. The same goes for anyone of unknown GBS status or anyone who didn't get treated enough times during labor. So why bother?
Also there are studies that none of this is really effective anyway.