As everybody has said, it's a normal part of your vaginal flora. I was on the fence about taking the antibiotics during labor (there is some serious question about whether it is necessary and/or smart to give them preventative) but I wanted to go home home right away after giving birth, so I decided to get it.
For me it was not a big deal. My water broke first so I made my way to the hospital to get the IV and then went home to wait for labor to start (I wanted to labor at home).
My daughter was born within 8 hours of the antibiotics IV so I never got a second dose. Had I been in labor longer they would have given a dose every 8 hours. I was released from the hospital with my daughter the same day she was born (no overnight stay) as I had wanted.