A 26-year-old woman in her 37th week of pregnancy tested positive for Group B Streptococcus (GBS). To prevent passing the infection to her newborn, which antibiotic class is appropriate?

Choice A reason: This is correct. Penicillin and other beta-lactams are the first-line antibiotics for intrapartum prophylaxis against GBS, effectively reducing vertical transmission to the newborn. Choice B reason: Aminoglycosides are not first-line for GBS prophylaxis; they have limited efficacy in this setting and potential maternal and fetal toxicity. Choice C reason: Sulfonamides are contraindicated late in pregnancy due to risks such as kernicterus in the newborn. Choice D reason: Fluoroquinolones are not recommended in pregnancy because of potential adverse effects on fetal cartilage development.