What is the recommended management for Group B streptococcus (GBS) during pregnancy?

Management of Group B Streptococcus (GBS) During Pregnancy

All pregnant women should undergo universal vaginal-rectal screening for GBS colonization at 36 0/7 to 37 6/7 weeks' gestation, with intrapartum antibiotic prophylaxis administered to all colonized women during labor. 1

Screening Protocol

Timing and Technique

• Screen between 36 0/7 and 37 6/7 weeks' gestation (updated from the previous 35-37 week window) 1, 2
• Collect specimens by swabbing the lower vagina (2 cm deep) and rectum (1 cm through the anal sphincter) 2, 3
• Do not use speculum examination for specimen collection 2
• Patients may perform their own swabs with appropriate instruction 2, 3
• Place specimens in non-nutritive transport medium (Amies or Stuart's without charcoal) 2
• Culture results remain valid for 5 weeks from collection 2

Laboratory Processing

• Inoculate specimens into selective broth medium, incubate overnight, and subculture onto blood agar 2
• For penicillin-allergic patients, perform susceptibility testing for clindamycin and erythromycin 2
• Laboratories should report results to both the ordering provider and anticipated delivery site 2

Indications for Intrapartum Antibiotic Prophylaxis (IAP)

Automatic Indications (No Screening Required)

• GBS bacteriuria at any concentration during current pregnancy - these women are heavily colonized and at increased risk 2
• Previous infant with invasive GBS disease - no screening needed, give IAP automatically 2

Screening-Based Indications

• Positive vaginal-rectal culture at 36-37 weeks 2, 1
• Unknown GBS status at labor onset with any of these risk factors: 2
  • Delivery at <37 weeks' gestation
  • Membrane rupture ≥18 hours
  • Intrapartum temperature ≥100.4°F (≥38.0°C)

When IAP Is NOT Required

• Planned cesarean delivery before labor onset with intact membranes at any gestational age, regardless of GBS status 2
• Negative GBS culture within 5 weeks of delivery, even if risk factors develop 2

Antibiotic Regimens

First-Line Agents

• Penicillin G: 5 million units IV initial dose, then 2.5-3 million units IV every 4 hours until delivery 2
• Ampicillin: 2 g IV initial dose, then 1 g IV every 4 hours until delivery (acceptable alternative) 2

Penicillin Allergy Management

• For patients with minor/non-anaphylactic allergy: Cefazolin 2 g IV initial dose, then 1 g IV every 8 hours 4
• For patients at risk of anaphylaxis (history of anaphylaxis, angioedema, respiratory distress, or urticaria to penicillin): 4
  • If GBS susceptible to clindamycin: Clindamycin 900 mg IV every 8 hours
  • If clindamycin-resistant or susceptibility unknown: Vancomycin 1 g IV every 12 hours
• Consider penicillin allergy skin testing during pregnancy, as confirmation or delabeling provides both short- and long-term health benefits 5, 3

Duration and Timing

• Adequate prophylaxis requires ≥4 hours of antibiotics before delivery for maximum effectiveness 1
• Minimum 2 hours of antibiotics reduces GBS vaginal colony counts and decreases clinical neonatal sepsis 1
• Do not delay necessary obstetric interventions solely to achieve 4 hours of antibiotic administration 1

Preterm Labor Management (<37 Weeks)

Initial Approach

• Obtain vaginal-rectal swab and start GBS prophylaxis immediately upon admission with signs/symptoms of preterm labor, unless GBS culture performed within preceding 5 weeks 2
• If patient had positive GBS screen within 5 weeks, give IAP 2
• If patient had negative GBS screen within 5 weeks, no IAP needed 2

Ongoing Management

• If true labor confirmed: Continue GBS prophylaxis until delivery 2
• If not in true labor: Discontinue GBS prophylaxis immediately 2
• If culture returns negative: Discontinue prophylaxis 2
• If patient reaches 36-37 weeks without delivering: Repeat vaginal-rectal culture 2

Preterm Premature Rupture of Membranes (PPROM)

• Obtain vaginal-rectal swab for GBS culture at admission 2
• Antibiotics given for latency (ampicillin 2 g IV, then 1 g IV every 6 hours for ≥48 hours) are adequate for GBS prophylaxis 2
• If entering labor with positive GBS status, give GBS prophylaxis 2
• If entering labor with negative GBS status, no GBS prophylaxis needed but repeat culture if reaches 36-37 weeks 2

Critical Pitfalls to Avoid

• Do not treat asymptomatic GBS colonization with antibiotics before labor - this does not eliminate carriage or prevent neonatal disease and can cause adverse consequences 2
• Do not assume previous pregnancy GBS status applies - colonization status changes between pregnancies, requiring screening in each pregnancy 2
• Do not skip screening for planned cesarean deliveries - labor or membrane rupture can occur before planned surgery, necessitating IAP 2
• Do not use cervical cultures - only lower vaginal and rectal specimens are appropriate 2
• Do not withhold perioperative antibiotics for cesarean based on GBS status - these serve different purposes 2

Communication and Documentation

• Inform all women of their GBS screening results and recommended interventions 2
• Develop information systems ensuring prenatal culture results are available at delivery site 2
• Clearly label specimens to indicate pregnancy status and penicillin allergy when applicable 2