Group B strep

Just got a call that I was strep B positive on my urine culture. I will be starting an antibiotic and 7 weeks pregnant. My OB was not in the office for me to ask questions but wouldn’t you normally just get IV antibiotics during labor? Is this something I should be concerned about? Can’t it come and go? So why would a week of antibiotics do anything? Thanks in advance! FTM Mom here!!