Final answer:
The recommended drug to prevent Group B strep during pregnancy is intravenous penicillin. Alternatives include erythromycin or clindamycin, based on susceptibility, and vancomycin in case of high-level resistance or significant allergies.
Step-by-step explanation:
The most widely recommended drug for the prevention of Group B streptococcal (GBS) infection during pregnancy is intravenous penicillin. If a patient has an allergy to penicillin, alternative antibiotics such as erythromycin or clindamycin could be considered, after testing for susceptibility. In the case of high-level resistance to these alternatives, or if the patient has a significant allergy, vancomycin is sometimes used. It's important to consult with healthcare providers for the most up-to-date recommendations and susceptibility testing results for each case.