What is the best course of action for a woman in active labor, 8 cm dilated, with a Group B Streptococcus (GBS) infection who has not received intravenous (IV) antibiotics?

Administer IV Antibiotics Immediately

Even at 8 cm dilation in active labor, intravenous antibiotic prophylaxis should be administered immediately to a GBS-positive woman who has not yet received antibiotics. While the window for optimal prophylaxis (≥4 hours before delivery) may be limited, any duration of intrapartum antibiotics provides some protection against early-onset neonatal GBS disease and should not be withheld. 1, 2

Rationale for Immediate IV Antibiotic Administration

Effectiveness Even with Short Duration

• Beta-lactam prophylaxis administered for 2 to <4 hours before delivery still provides 47% effectiveness against early-onset GBS disease, and even <2 hours provides 38% effectiveness, though both are significantly lower than the 86-91% effectiveness achieved with ≥4 hours of prophylaxis. 3

• The CDC explicitly recommends continuing prophylaxis until delivery regardless of how advanced labor has progressed, as some protection is better than none. 1, 2

Recommended Antibiotic Regimen

For non-penicillin allergic patients:

• Penicillin G: 5 million units IV initially, then 2.5-3.0 million units IV every 4 hours until delivery (preferred due to narrow spectrum). 1, 2, 4
• Ampicillin: 2 g IV initially, then 1 g IV every 4 hours until delivery (acceptable alternative). 1, 2

For penicillin-allergic patients without high-risk features (no history of anaphylaxis, angioedema, respiratory distress, or urticaria):

• Cefazolin: 2 g IV initially, then 1 g IV every 8 hours until delivery (preferred alternative). 1, 2

For penicillin-allergic patients at high risk for anaphylaxis:

• Clindamycin: 900 mg IV every 8 hours until delivery (if susceptibility confirmed). 1, 5
• Vancomycin: 1 g IV every 12 hours until delivery (if susceptibility unknown or resistant to clindamycin). 1, 6

Why Other Options Are Incorrect

Cesarean Section (C/S) is NOT Indicated

• GBS colonization alone is not an indication for cesarean delivery. Obstetric procedures should not be altered based solely on GBS status. 1
• Cesarean section does not eliminate the risk of vertical GBS transmission and would expose the mother to unnecessary surgical risks. 2

IM Antibiotics Are NOT Appropriate

• Intravenous administration is the only recommended route for intrapartum GBS prophylaxis because it achieves higher intraamniotic concentrations necessary for effective prevention. 1
• While some observational studies showed benefit from IM penicillin given to newborns postpartum, this is not the standard approach and does not replace maternal intrapartum prophylaxis. 1

"Do Nothing" is NOT Acceptable

• Withholding antibiotics because labor is advanced contradicts CDC guidelines, which recommend prophylaxis be administered until delivery regardless of cervical dilation. 1, 2
• Even partial prophylaxis reduces neonatal risk and is the standard of care. 3

Neonatal Management Implications

Because this infant will receive <4 hours of maternal prophylaxis, the newborn management will be affected:

• Well-appearing term infants (≥37 weeks) born to mothers who received <4 hours of adequate GBS prophylaxis require observation for ≥48 hours. 1
• If the infant is preterm (<37 weeks) or membranes were ruptured ≥18 hours, a limited evaluation (blood culture and CBC at birth and/or 6-12 hours) plus observation for ≥48 hours is indicated. 1

Critical Pitfalls to Avoid

• Never delay or withhold antibiotics based on advanced cervical dilation—some protection is always better than none. 1, 2
• Do not use oral antibiotics or IM routes—only IV administration achieves adequate intraamniotic levels. 1
• Clindamycin effectiveness is significantly lower (22%) compared to beta-lactams, so it should only be used when penicillin allergy is documented and susceptibility is confirmed. 3, 7
• Ensure the neonatal team is aware of inadequate prophylaxis duration (<4 hours) so appropriate newborn monitoring can be implemented. 1