As RainbowBrite says, it is only if your waters have been broken for 24 - 48 hours that antibiotics are likely to be suggested. If you say no, then the alternative is to track your body temperature to look for signs of infection and deal with them if they occur. Most OB's also highly recommend antibiotics if you have tested positive for group B strep, but again if you choose to refuse then you can monitor your baby post birth for signs of infection and deal with them if the occur. The risk, of course, is that once a newborn gets an infection they can go downhill very fast. However most babies born to mothers who are + for GBS (and to mothers whose waters break early) do fine with no infection.