Hi, popping on over from first tri, but wanted to share my first birth story with you because during my first pregnancy I was Group Strep B positive, and I actually am allergic to penecillin.
Whenever I had an OB appointment, I would always fill out the paper stating I was allergic to that med, so my Doctor always saw it, and during the weeks prior to giving birth, I had made sure that my doctor had put it down on the record that I was positive for Group Strep B, and that she had also put down that I was allergic to the standard medicine they gave during labor to help curb it, which happened to be, penecillin, surprise surprise. I had asked her what they would do with me as I was allergic to penecillin, but she had told me that they would just give a different medication through an IV during my labor that would be just as effective.
Fast forward to 40 weeks and 3 days and I was in labor. When they admitted me, they gave an IV through the arm that was held up on one of those poles. It did make mobility a bit more challenging, but I was still able to get around and use the bathroom as needed. Went on to give birth vaginally to a perfect and healthy little girl. She never had any side effects form the meds, and to this day is thriving very well, she's actually pretty advanced for her age. Try not to worry

I'm sure it will be fine. I was also quite worried when I first got the news, but it really turned out to be almost no big deal at all, and a very minor issue that was easily taken care of.
If you have taken penecillin in the past without an issue, I don't think it will cause a problem for you this time either, but if you do have reactions, it might be worth mentioning to your doctor as they are the ones who can assess the situation the best. Since I was given a different med during my labor, I had no reaction at all, and went on to have a normal labor without any complications or side effects to me or my baby