Which antibiotic is commonly used intrapartum for GBS prophylaxis in most cases?

• A. Penicillin G
• B. Ampicillin
• C. Erythromycin
• D. Azithromycin

Answer: (A)

Intrapartum prophylaxis aims to prevent early newborn infection by giving antibiotics during labor to mothers who carry Group B Streptococcus. The best choice is Penicillin G because it reliably covers GBS, has a narrow spectrum that minimizes disruption to normal flora, and transfers well to the fetus during labor, providing effective protection with a strong safety profile for both mother and baby. It is typically given intravenously during labor and continued until delivery. Macrolides like erythromycin or azithromycin are less reliable due to rising resistance and are not used as first-line prophylaxis. Ampicillin can be used if Penicillin G isn’t available or in certain allergy scenarios, but Penicillin G remains the most commonly used agent in most cases.