What is the recommended treatment for Group B strep (Streptococcus agalactiae) during labor?

Treatment of Group B Streptococcus (GBS) During Labor

Penicillin G is the first-line treatment for intrapartum Group B streptococcal prophylaxis, administered as 5 million units IV initial dose, followed by 2.5-3.0 million units IV every 4 hours until delivery. 1

First-Line Treatment Options

• Penicillin G: 5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours until delivery 1
• Ampicillin: 2 g IV initial dose, then 1 g IV every 4 hours until delivery (acceptable alternative) 1

Management for Penicillin-Allergic Women

Low Risk for Anaphylaxis (no history of anaphylaxis, angioedema, respiratory distress, or urticaria):

• Cefazolin: 2 g IV initial dose, then 1 g IV every 8 hours until delivery 1

High Risk for Anaphylaxis (history of anaphylaxis, angioedema, respiratory distress, or urticaria):

• If GBS isolate is susceptible to clindamycin and erythromycin:
  • Clindamycin: 900 mg IV every 8 hours until delivery 1
• If GBS isolate is resistant to clindamycin or susceptibility is unknown:
  • Vancomycin: 1 g IV every 12 hours until delivery 1

Indications for Intrapartum GBS Prophylaxis

Intrapartum antibiotic prophylaxis is indicated for women with:

• Positive GBS vaginal-rectal screening culture at 35-37 weeks' gestation 1
• GBS bacteriuria during the current pregnancy (regardless of colony count) 1
• Previous infant with invasive GBS disease 1
• Unknown GBS status at labor onset with any of these risk factors:
  • Delivery at <37 weeks' gestation
  • Amniotic membrane rupture ≥18 hours
  • Intrapartum temperature ≥100.4°F (≥38.0°C) 1

Special Considerations

Preterm Labor

• Women with signs/symptoms of preterm labor (<37 weeks) should be screened for GBS colonization at hospital admission unless screening was performed within the preceding 5 weeks 1
• Start GBS prophylaxis at hospital admission for women with unknown GBS status or positive GBS screen 1
• Discontinue antibiotics if not in true labor; resume at onset of true labor if GBS positive 1

Premature Rupture of Membranes (PROM)

• For women with PROM at <37 weeks: obtain vaginal-rectal GBS culture and start antibiotics for latency or GBS prophylaxis 1
• For women with PROM at ≥37 weeks who are GBS positive: administer IV GBS prophylaxis and proceed with immediate obstetrical delivery 2

Cesarean Delivery

• Routine intrapartum antibiotic prophylaxis for GBS is not recommended for women undergoing planned cesarean delivery performed before onset of labor with intact membranes, regardless of GBS colonization status 1

Timing Considerations

• Intrapartum antibiotic prophylaxis is optimal if administered for at least 4 hours before delivery 1
• However, obstetric interventions should not be delayed solely to provide 4 hours of antibiotic administration 1, 3

Neonatal Management

• Any newborn with signs of sepsis should receive a full diagnostic evaluation and antibiotic therapy 1
• Well-appearing newborns whose mothers had suspected chorioamnionitis should undergo a limited evaluation and receive antibiotic therapy pending culture results 1
• Management of asymptomatic newborns should follow the algorithm based on maternal GBS status, adequacy of prophylaxis, gestational age, and duration of membrane rupture 1

Common Pitfalls to Avoid

• Erythromycin is no longer an acceptable alternative for intrapartum GBS prophylaxis for penicillin-allergic women 1
• Do not use oral antibiotics to eradicate GBS colonization before labor, as this is ineffective 1
• Do not delay medically necessary obstetric procedures to achieve 4 hours of GBS prophylaxis 1
• Do not administer routine GBS prophylaxis for planned cesarean delivery with intact membranes before labor onset 1

The implementation of universal GBS screening and appropriate intrapartum antibiotic prophylaxis has significantly reduced the incidence of early-onset neonatal GBS disease 3, 4, making this one of the most successful preventive strategies in perinatal medicine.