Group B Streptococcus in Pregnancy

1. Clinical Overview

Group B Streptococcus (GBS, Streptococcus agalactiae) is a gram-positive, β-hemolytic bacterium that colonizes the gastrointestinal and genitourinary tracts of approximately 18-20% of pregnant women worldwide. [1,2] While usually harmless to the mother, GBS is the leading cause of early-onset neonatal sepsis (EONS) in developed countries, causing life-threatening infection in newborns including septicemia, pneumonia, and meningitis. [3,4]

Vertical transmission occurs during labour and delivery when the neonate is exposed to GBS in the maternal genital tract. Without prophylactic intervention, approximately 50% of infants born to colonized mothers become colonized, and 1-2% of these colonized neonates develop invasive early-onset disease. [5] The implementation of universal antenatal screening and intrapartum antibiotic prophylaxis (IAP) strategies has reduced EONS incidence by 80-90%, from 1.7 per 1000 live births in the 1990s to 0.23 per 1000 live births currently in the United States. [3,5]

Key Clinical Message: GBS in pregnancy represents a critical intersection of maternal colonization, neonatal vulnerability, and preventable severe infection. Recognition of risk factors and timely administration of intrapartum antibiotics are the cornerstones of prevention, making GBS screening and prophylaxis protocols essential components of modern obstetric care.

Global Screening Strategies

Two major approaches exist worldwide:

• Universal Culture-Based Screening (USA, Canada, Australia): All pregnant women screened at 35-37 weeks gestation with vaginal-rectal swabs. IAP given to all carriers. [5,6]
• Risk-Based Approach (UK, Netherlands, Denmark): No routine screening. IAP given based on clinical risk factors (previous GBS-affected infant, GBS bacteriuria, preterm labour, prolonged rupture of membranes, intrapartum fever). [7,8]

Both strategies have merits and limitations, with ongoing debate about optimal prevention methodology. [9]

---

2. Epidemiology

Maternal Colonization

Exam Detail: Global Colonization Rates: A systematic review of 390 studies involving 299,924 pregnant women across 85 countries revealed a global maternal GBS colonization prevalence of 18% (95% CI 17-19%), with significant regional variation. [2]

UK-Specific Data: Approximately 20-25% of pregnant women in the UK are colonized with GBS. [7]

Colonization Characteristics:

• Intermittent Carriage: GBS colonization is dynamic and can change during pregnancy. Up to 40% of women who test positive at 35-37 weeks may be negative at delivery, and vice versa. [5,10]
• Heavy vs. Light Colonization: Heavy colonization is associated with higher transmission risk to the neonate. [11]

Neonatal Disease Burden

Exam Detail: Early-Onset Disease (EOD) (less than 7 days, typically less than 24 hours):

Late-Onset Disease (LOD) (7-90 days):

• Incidence: 0.3-0.4 per 1000 live births. [3]
• Not prevented by IAP – acquired postnatally from maternal, environmental, or nosocomial sources. [4]

Mortality and Morbidity:

• EOD Mortality: 5-10% in term infants; up to 20-30% in preterm infants. [3,13]
• Meningitis: Occurs in 5-10% of EOD cases. Among survivors, 20-30% suffer long-term neurological sequelae including cerebral palsy, developmental delay, hearing loss, and seizures. [14]
• LOD Mortality: Similar to EOD (5-10%), with higher meningitis rate (30-40% of LOD cases). [14]

Maternal Disease

GBS causes maternal infections less frequently but can result in:

• GBS Bacteriuria: 2-7% of pregnant women; associated with heavy colonization and higher neonatal infection risk. [15]
• Chorioamnionitis: GBS accounts for 5-10% of cases. [16]
• Postpartum Endometritis: 5-10% attributable to GBS. [16]
• Bacteremia/Sepsis: Rare but can occur, particularly with chorioamnionitis. [1]

---

3. Microbiology & Pathophysiology

Microbiology

Exam Detail: Organism: Streptococcus agalactiae (Lancefield Group B Streptococcus)

• Gram-positive coccus, forming chains
• β-hemolytic on blood agar
• Catalase-negative
• Produces CAMP factor (Christie-Atkins-Munch-Petersen test positive)
• Hydrolyzes hippurate and sodium bile esculin

Capsular Serotypes: Ten capsular polysaccharide types have been identified (Ia, Ib, II, III, IV, V, VI, VII, VIII, IX). [1,2]

Virulence Factors: [1,18]

• Capsular polysaccharide: Antiphagocytic; serotype III particularly neurovirulent
• β-hemolysin/cytolysin (β-H/C): Disrupts host cell membranes, induces inflammation, crosses blood-brain barrier
• Surface proteins: C protein (α, β, Rib), pili, adhesins for attachment to host cells
• Hyaluronidase: Facilitates tissue invasion

Transmission Pathways

Vertical Transmission (Mother-to-Neonate):

1. Ascending Infection: After rupture of membranes, GBS ascends from the vagina into the amniotic cavity. [1]
2. Intrapartum Exposure: Neonate is exposed to GBS in the birth canal during vaginal delivery. [5]
3. In Utero Infection: Rare; can occur with intact membranes, leading to stillbirth or early neonatal infection. [19]

Horizontal Transmission (LOD):

• Maternal breast milk (controversial – some studies positive, others negative). [20]
• Healthcare worker hands, environmental surfaces in neonatal units. [14]
• Community acquisition. [14]

Neonatal Pathogenesis

Exam Detail: Early-Onset Disease (less than 7 days):

The neonate acquires GBS during passage through the colonized birth canal or via ascending infection. Risk of progression to invasive disease depends on:

1. Maternal Factors:

   • Inoculum size: Heavy maternal colonization increases transmission risk. [11]
   • Absence of serotype-specific antibodies: Maternal IgG antibodies cross the placenta and provide passive immunity. Low maternal antibody levels correlate with increased neonatal risk. [21]

2. Neonatal Factors:

   • Prematurity: Preterm infants (less than 37 weeks) have immature immune systems and lower transplacental antibody transfer. [22]
   • Low birth weight: less than 2500g associated with higher risk. [5]

3. Obstetric Factors:

   • Prolonged rupture of membranes (> 18 hours): Allows ascending infection. [5]
   • Intrapartum fever: Suggests intraamniotic infection and inflammation. [5]

Late-Onset Disease (7-90 days):

Acquisition occurs after birth from maternal or environmental sources. Pathogenesis differs:

• Higher rate of meningitis (30-40% vs. 5-10% in EOD). [14]
• Serotype III predominates (> 75% of LOD cases). [14]
• Often affects previously healthy, term infants without obvious risk factors. [14]

Clinical Manifestations:

• Septicemia: Fever, lethargy, poor feeding, tachypnea, hypotension, shock
• Pneumonia: Respiratory distress, hypoxemia, chest X-ray infiltrates
• Meningitis: Bulging fontanelle, seizures, irritability, CSF pleocytosis, positive culture

---

4. Risk Factors for Neonatal Early-Onset Disease

Major Risk Factors

Exam Detail: The following factors significantly increase risk of neonatal EOD and form the basis for risk-based IAP strategies:

Risk Stratification

High Risk (Multiple risk factors or single major risk factor):

• Previous GBS-affected infant
• GBS bacteriuria in current pregnancy
• Preterm labour + any additional risk factor

Moderate Risk (Single risk factor):

• Positive GBS culture alone
• PROM > 18 hours at term
• Intrapartum fever

Low Risk:

• Negative GBS culture at 35-37 weeks
• Planned caesarean section before labour and membrane rupture

---

5. Clinical Presentation

Maternal Presentation

Asymptomatic Colonization (Majority):

• No symptoms
• Detected by screening culture or incidentally

Symptomatic Maternal Infections (Uncommon):

Neonatal Presentation

Exam Detail: Early-Onset Disease (less than 7 days, usually less than 24 hours):

Onset: Median age 1 hour; 90% present within first 24 hours. [3,13]

Clinical Features:

Chest X-ray in EOD Pneumonia:

• Bilateral infiltrates, often indistinguishable from respiratory distress syndrome (RDS)
• Can mimic surfactant deficiency in preterm infants [13]

Late-Onset Disease (7-90 days):

Onset: Median age 24 days (range 7-89 days). [14]

Clinical Features:

• Meningitis: 30-40% of LOD cases [14]
  • Fever, irritability, poor feeding, lethargy
  • Bulging fontanelle, seizures, abnormal tone
  • "CSF: Pleocytosis (typically > 1000 WBC/μL, neutrophil predominance), elevated protein, low glucose"
• Bacteremia without focal infection: 50-60% [14]
• Focal infections: Osteomyelitis, septic arthritis, cellulitis (10-20%) [14]

Red Flag Signs in Neonate:

• Respiratory distress (grunting, retractions, tachypnea > 60/min)
• Lethargy or irritability
• Temperature instability (less than 36°C or > 38°C)
• Poor feeding or vomiting
• Apnea or cyanosis
• Seizures

---

6. Investigations

Maternal Investigations

Exam Detail: GBS Screening Culture (Universal Screening Approach):

Timing: 35 weeks 0 days to 37 weeks 6 days gestation (CDC, ACOG guidelines). [5,6]

Rationale for Timing:

• Performed close to delivery to maximize correlation with intrapartum colonization status
• Sensitivity decreases significantly if performed > 5 weeks before delivery [23]

Collection Technique:

• Lower vaginal swab (introitus or lower one-third of vagina) AND rectal swab (through anal sphincter)
• Combined vaginal-rectal sampling increases sensitivity by ~25% vs. vaginal alone [23]
• No speculum required for vaginal swab (self-collection acceptable)

Laboratory Processing:

• Enriched selective broth media (e.g., Todd-Hewitt broth, Lim broth with selective antibiotics)
• Subculture to blood agar after 18-24 hours incubation
• Identification via colony morphology, β-hemolysis, CAMP test, latex agglutination, or MALDI-TOF
• Antimicrobial susceptibility testing if penicillin allergy with anaphylaxis risk (test clindamycin susceptibility)

Rapid Intrapartum Tests:

• PCR-based NAAT (Nucleic Acid Amplification Tests): Results in 1-3 hours; can be used intrapartum if no prenatal screening performed [24]
• Sensitivity ~95%, specificity ~98% [24]
• Useful for women presenting in labour without documented GBS status

Urine Culture:

• Routinely performed in early pregnancy
• If GBS detected in urine at any colony count, treat the UTI and provide IAP during labour [5,15]

UK Risk-Based Approach (No Routine Screening): [7]

• Swabs only performed if clinically indicated (e.g., suspected UTI, previous GBS-affected infant)
• IAP given based on risk factors (see Management section)

Neonatal Investigations

Exam Detail: Indications for Septic Screen:

• Neonate with clinical signs of sepsis (respiratory distress, lethargy, temperature instability, poor feeding)
• Maternal risk factors + inadequate IAP + clinical concerns

Septic Screen Components:

CSF Findings in GBS Meningitis: [14]

• White cell count: > 1000 cells/μL (typically neutrophil predominance)
• Protein: > 1.0 g/L (often > 2 g/L)
• Glucose: less than 2.2 mmol/L (CSF:blood glucose ratio less than 0.6)
• Gram stain: Gram-positive cocci in chains (50-60% sensitivity)
• Culture: Positive for GBS (gold standard)

Procalcitonin (PCT): Emerging biomarker; may be more sensitive than CRP in early sepsis. [25]

Risk Stratification Tools:

Kaiser Permanente Neonatal Sepsis Calculator: [26]

• Online tool incorporating maternal risk factors, clinical presentation, and lab results
• Calculates individualized sepsis risk and provides management recommendations
• Updated in 2024 with contemporary cohort data (2010-2020) [26]
• Sensitivity 0.80 (95% CI 0.68-0.89) for identifying EOD cases [26]
• Reduces unnecessary antibiotic exposure by ~50% vs. traditional risk factor-based algorithms [26]

---

7. Management

Intrapartum Antibiotic Prophylaxis (IAP)

IAP is the cornerstone of EOD prevention, reducing incidence by 80-90%. [3,5]

Exam Detail: #### Indications for IAP

Universal Screening Approach (USA, Canada, Australia): [5,6]

Risk-Based Approach (UK - RCOG Green-top Guideline 36): [7]

Exception – IAP NOT Required: [5,7]

• Planned caesarean section before onset of labour AND with intact membranes (very low transmission risk)

IAP Antibiotic Regimens

Exam Detail: First-Line Regimen (No Penicillin Allergy): [5,7]

BENZYLPENICILLIN (Penicillin G)
- Loading dose: 3 g IV (some sources use 5 million units IV)
- Maintenance: 1.5 g IV every 4 hours until delivery

Alternative: AMPICILLIN
- Loading dose: 2 g IV
- Maintenance: 1 g IV every 4 hours until delivery

Penicillin Allergy – NON-Anaphylactic (e.g., rash): [5,7]

CEFAZOLIN (if cephalosporin tolerance)
- Loading dose: 2 g IV
- Maintenance: 1 g IV every 8 hours until delivery

OR

CEFUROXIME (UK alternative)
- 1.5 g IV every 8 hours until delivery

Penicillin Allergy – ANAPHYLACTIC (e.g., angioedema, anaphylaxis, urticaria): [5,7]

If GBS susceptibility testing shows clindamycin sensitivity:

CLINDAMYCIN
- 900 mg IV every 8 hours until delivery

If GBS clindamycin-resistant OR susceptibility unknown:

VANCOMYCIN
- 1 g IV every 12 hours until delivery

Note: Clindamycin resistance in GBS varies geographically (10-40%). [5] Inducible clindamycin resistance (erm gene) should be tested via D-test. [5]

IAP Timing and Adequacy

Exam Detail: Optimal Timing: [5,27]

• IAP should be initiated at onset of labour or rupture of membranes, whichever occurs first
• Adequate IAP defined as ≥4 hours of antibiotic administration before delivery [5,27]
  • ≥4 hours: ~90% reduction in EOD risk
  • 2-4 hours: ~50-70% reduction in EOD risk
  • less than 2 hours: Limited efficacy (~20-30% reduction)

Key Principle: [5]

"Obstetric interventions should NOT be delayed solely to achieve 4 hours of antibiotic administration."

• Proceed with delivery if clinically indicated (e.g., fetal compromise, maternal indication)
• Even less than 4 hours IAP provides some protection and reduces GBS vaginal colony counts [27]

Situations Requiring IAP Initiation:

• Onset of regular contractions (labour)
• Artificial rupture of membranes for induction
• Spontaneous rupture of membranes (even if no contractions)

IAP Not Indicated:

• External cephalic version (no labour or membrane rupture)
• Previable PPROM less than 24 weeks (antibiotics for other indications may be given)

Special Situations

Exam Detail: Precipitate Delivery (Delivery imminent, no time for IV access):

• Attempt IV access and give at least loading dose if possible
• Neonate considered at higher risk; requires enhanced observation [7]

Planned Caesarean Section:

• If performed before labour onset and membranes intact: IAP not required [5,7]
• If labour begins or membranes rupture before caesarean: IAP indicated as per usual criteria [5,7]

Suspected Chorioamnionitis: [5,16]

• Use broad-spectrum antibiotics (e.g., ampicillin + gentamicin, or co-amoxiclav) rather than penicillin alone
• Covers GBS and other pathogens (E. coli, anaerobes)

PPROM (Preterm Prelabour Rupture of Membranes):

• less than 37 weeks: Give IAP (unless GBS known negative within 5 weeks) [7,22]
• Also give: Erythromycin for 10 days to prolong latency (ORACLE trial) [22]
• If labour ensues: Continue/restart IAP (benzylpenicillin or ampicillin)

Neonatal Management

Exam Detail: Neonatal management depends on maternal risk factors, adequacy of IAP, and clinical condition of the neonate. [7,13]

Well-Appearing Neonate, Adequate IAP (≥4 hours)

Observation:

• Clinical observation for 12-24 hours in hospital [7]
• Monitor: Temperature, respiratory rate, feeding, activity, color
• No routine laboratory investigations or antibiotics

Well-Appearing Neonate, Inadequate IAP (less than 4 hours) OR Risk Factors

Enhanced Observation:

• Minimum 24 hours observation [7]
• Consider baseline investigations (FBC, CRP) if multiple risk factors
• Some centers use neonatal sepsis calculators to individualize management [26]

Symptomatic Neonate (Any Signs of Sepsis)

Immediate Action: [13,25]

1. Full septic screen:

   • Blood culture (from peripheral vein, NOT umbilical catheter if possible – higher contamination)
   • FBC, CRP (repeat CRP at 24-48h)
   • Lumbar puncture (if stable enough to tolerate procedure; defer if critically unwell, perform when stabilized)
   • Chest X-ray if respiratory signs

2. Empirical antibiotics (start immediately after cultures obtained):

   BENZYLPENICILLIN (or AMPICILLIN)
   + GENTAMICIN
   
   Benzylpenicillin: 50 mg/kg IV every 12h (less than 7 days), every 8h (> 7 days)
   Gentamicin: Dose per local protocol (typically 4-5 mg/kg once daily)
   

3. Supportive care:

   • Respiratory support (oxygen, CPAP, mechanical ventilation as needed)
   • Fluid resuscitation and inotropes for shock
   • Correct hypoglycemia, electrolyte abnormalities
   • Temperature regulation (incubator/radiant warmer)

4. Duration of antibiotics:

   • If blood culture negative and clinical improvement: Stop antibiotics at 36-48 hours [13]
   • If blood culture positive (confirmed GBS sepsis):
     • Without meningitis: 10 days IV antibiotics [13]
     • With meningitis: 14-21 days IV antibiotics (minimum 14 days; longer if complicated) [14]
   • Switch to Benzylpenicillin alone (or Ampicillin) once GBS confirmed (narrow spectrum, avoid gentamicin toxicity) [13]

5. Lumbar puncture timing:

   • Perform LP if blood culture positive OR clinical suspicion of meningitis (irritability, seizures, bulging fontanelle) [14]
   • Repeat LP after 24-48 hours of treatment to confirm CSF sterilization (if initial CSF culture positive) [14]

Risk-Based vs. Calculator-Based Approaches

Traditional Risk-Based: All neonates with maternal risk factors + inadequate IAP receive empirical antibiotics. [7]

Sepsis Calculator-Based: [26]

• Incorporates maternal risk factors, clinical examination, and objective clinical illness scores
• Provides individualized sepsis risk estimate and treatment recommendation
• Can safely reduce antibiotic use by ~50% compared to traditional algorithms [26]
• Requires adherence to protocol, serial examinations, and parental education

---

8. Prevention Strategies

Primary Prevention (Reducing Colonization)

Maternal Vaccination:

• GBS vaccines targeting capsular polysaccharides (serotypes Ia, Ib, II, III, V) are in development. [28]
• Hexavalent conjugate vaccines show promise in Phase 1/2 trials. [28]
• Goal: Induce maternal antibodies that cross placenta and protect neonate (passive immunity). [21,28]
• Potential advantages: Would prevent EOD and LOD; reduce IAP use and antibiotic resistance concerns. [28]

Probiotics:

• Lactobacillus rhamnosus GR-1 and other probiotic strains studied for reducing GBS colonization. [29]
• Evidence limited and inconsistent; not currently recommended in guidelines. [29]

Secondary Prevention (Intrapartum Antibiotics)

IAP Effectiveness: [3,5,27]

• Reduces EOD by 80-90%
• Most effective with adequate duration (≥4 hours)
• Does not prevent LOD (antibiotic only present during labour)

Limitations of IAP:

• Overtreatment (~30-40% of women in USA receive antibiotics; many with negative GBS status at delivery due to transient colonization) [5,10]
• Antibiotic resistance concerns (selection pressure for resistant organisms) [30]
• Anaphylaxis risk (rare but serious)
• Disruption of neonatal microbiome (potential long-term effects on immunity, allergies, obesity – under investigation) [31]

Tertiary Prevention (Early Detection and Treatment)

Neonatal Surveillance:

• Early recognition of signs of sepsis
• Prompt septic screen and empirical antibiotics

Education:

• Parental education on warning signs (poor feeding, lethargy, respiratory distress, fever)
• Healthcare professional training on sepsis recognition and management

---

9. Complications

Neonatal Complications

Exam Detail: | Complication | Frequency | Long-Term Sequelae | Management | |--------------|-----------|-------------------|------------| | Septicemia | 90-95% of EOD [13] | Rare if treated promptly | IV antibiotics, supportive care | | Pneumonia | 80-90% of EOD [13] | Chronic lung disease (rare) | Respiratory support, antibiotics | | Meningitis | 5-10% EOD, 30-40% LOD [14] | 20-30% have neurological sequelae: cerebral palsy, developmental delay, hearing loss, seizures, hydrocephalus | Prolonged antibiotics (14-21 days), neurodevelopmental follow-up, hearing screening | | Shock/Multi-organ Failure | 30-50% severe sepsis [13] | Death (5-10% EOD mortality) | Inotropes, ventilation, renal support | | Death | 5-10% (higher in preterm) [3,13] | N/A | Intensive care, family support |

Neurological Outcomes After GBS Meningitis: [14]

• 20-30% survivors have moderate-to-severe disability:
  • "Cerebral palsy: 10-15%"
  • "Developmental delay (cognitive, motor): 15-20%"
  • "Hearing loss (sensorineural): 5-10%"
  • "Seizure disorder: 5-10%"
  • "Hydrocephalus requiring shunt: 5%"
• All neonates with GBS meningitis require:
  • Neurodevelopmental follow-up (6 months, 12 months, 2 years)
  • Hearing screening (auditory brainstem response before discharge and at 6 months)
  • MRI brain (to assess injury extent)

Maternal Complications

---

10. Prognosis

Neonatal Prognosis

Early-Onset Disease:

• With prompt treatment: 90-95% survival rate [3,13]
• Mortality: 5-10% in term infants; 20-30% in preterm/very low birth weight infants [13]
• Long-term morbidity: Most survivors without meningitis have normal neurodevelopment. Meningitis survivors: 20-30% have sequelae. [14]

Late-Onset Disease:

• Mortality: Similar to EOD (5-10%) [14]
• Higher meningitis rate (30-40%): Therefore, higher overall neurological morbidity risk [14]

Maternal Prognosis

• Asymptomatic colonization: Excellent; no long-term sequelae
• GBS infections (chorioamnionitis, endometritis): Resolve with antibiotics; rare progression to severe sepsis or death in modern settings
• Future pregnancies: Colonization status can change; screening recommended in each pregnancy [5]

---

11. Guidelines and Evidence

Key Guidelines

Exam Detail: 1. RCOG Green-top Guideline No. 36 (2017): Prevention of Early-Onset Neonatal Group B Streptococcal Disease [7]

• UK approach: Risk-based strategy (no universal screening)
• IAP indications: Previous GBS-affected infant, GBS bacteriuria, incidental GBS detection, preterm labour
• Does NOT recommend routine universal screening at 35-37 weeks

2. ACOG Committee Opinion No. 797 (2020): Prevention of Group B Streptococcal Early-Onset Disease in Newborns [5]

   • USA approach: Universal culture-based screening at 36 0/7 to 37 6/7 weeks
   • IAP for all GBS-positive women (unless elective caesarean before labour/membrane rupture)
   • Updates CDC 2010 guidelines

3. CDC Guidelines (2010, updated by ACOG 2020): [5,6]

   • Universal screening approach
   • IAP algorithms based on GBS status and risk factors

4. NICE Neonatal Infection Guideline (NG195) (2021): [25]

   • Risk factor-based approach to identifying at-risk neonates
   • Recommends observation, investigations, or antibiotics based on risk stratification

5. RANZCOG Guideline (Australia/New Zealand, 2016): [6]

   • Universal screening at 35-37 weeks (similar to USA approach)

Landmark Evidence

Exam Detail: 1. Schrag et al., NEJM 2000: [32]

• Demonstrated 80% reduction in EOD incidence with universal screening + IAP vs. risk-based approach alone
• Led to widespread adoption of universal screening in USA

2. Russell et al., CID 2017: [2]

   • Global systematic review and meta-analysis: 18% maternal colonization prevalence worldwide
   • Significant regional variation; lower in Asia (11-12.5%)

3. Manuel et al., CMR 2025: [1]

   • Comprehensive narrative review on GBS pathogenesis, virulence factors, and future prophylaxis (vaccines)

4. Tavares et al., CMR 2022: [14]

   • Detailed review of GBS neonatal meningitis: 20-30% neurological sequelae in survivors

5. Kuzniewicz et al., Pediatrics 2024: [26]

   • Updated EOS calculator using 2010-2020 data; sensitivity 0.80, reduces antibiotic use while maintaining safety

Controversies and Evolving Practice

Universal Screening vs. Risk-Based Approach:

• Universal screening (USA, Australia): More sensitive, prevents more EOD cases, but results in more antibiotic use (31% of women in USA receive IAP). [5,9]
• Risk-based (UK, Netherlands): Lower antibiotic use, but misses some cases (sensitivity ~60-70%). [7,9]
• Debate continues: Cost-effectiveness, antibiotic stewardship, impact on microbiome. [9]

Antibiotic Resistance:

• Increasing clindamycin and erythromycin resistance in GBS (10-40% depending on region). [30]
• Selection pressure for resistant E. coli and other pathogens in neonates (IAP may contribute). [30]

Maternal Vaccination:

• Most promising long-term strategy to prevent both EOD and LOD without antibiotics. [28]
• Several candidate vaccines in Phase 2/3 trials (hexavalent conjugate, trivalent conjugate). [28]
• Challenges: Serotype coverage, duration of immunity, cost-effectiveness. [28]

---

12. Examination Focus

Common MRCOG/Exam Questions

Exam Detail: 1. "What is your approach to GBS screening and prophylaxis in the UK?"

• Explain risk-based approach (no universal screening)
• Outline indications for IAP (previous GBS baby, GBS bacteriuria, incidental detection, preterm labour, consider for PROM > 18h and intrapartum fever)
• Discuss antibiotic regimens (benzylpenicillin first-line, alternatives for penicillin allergy)
• Mention that elective CS before labour/membrane rupture does not require IAP

2. "A woman presents in labour at 35 weeks with unknown GBS status. How would you manage?"

   • Give IAP (preterm labour is indication)
   • Use benzylpenicillin 3g IV loading, then 1.5g IV every 4 hours
   • Aim for ≥4 hours before delivery (but don't delay delivery if clinically indicated)
   • Inform neonatal team; neonate will need enhanced observation (12-24 hours minimum)
   • If penicillin allergy: Use alternative regimen (cefazolin, clindamycin, or vancomycin depending on allergy severity and GBS susceptibility)

3. "What is the difference between early-onset and late-onset GBS disease?"

   • EOD: less than 7 days (typically less than 24h); acquired intrapartum; presents as septicemia/pneumonia (5-10% meningitis); prevented by IAP
   • LOD: 7-90 days; acquired postnatally; higher meningitis rate (30-40%); NOT prevented by IAP; serotype III predominates

4. "What are the risk factors for early-onset neonatal GBS disease?"

   • Previous infant with invasive GBS disease (strongest single predictor)
   • GBS bacteriuria in current pregnancy
   • Positive GBS culture at 35-37 weeks
   • Preterm labour (less than 37 weeks)
   • Prolonged rupture of membranes (≥18 hours)
   • Intrapartum fever ≥38°C

5. "A woman had a positive GBS culture at 36 weeks. She presents for elective caesarean section at 39 weeks before labour. Does she need antibiotics?"

   • No – if caesarean performed before onset of labour AND membranes intact, transmission risk is negligible, so IAP not required [5,7]

Viva Scenarios

Viva Point: Scenario 1: Penicillin Allergy in GBS-Positive Woman

Examiner: "A 28-year-old woman is GBS-positive and reports a penicillin allergy. What do you need to know, and how will you manage?"

Model Answer: "I need to establish the nature and severity of the allergic reaction. I would ask:

• What reaction did she have? (Rash, urticaria, angioedema, anaphylaxis, breathing difficulty)
• When did it occur? (Immediate vs. delayed)

If non-anaphylactic (e.g., mild rash):

• I would offer cefazolin 2g IV loading, then 1g every 8 hours (or cefuroxime 1.5g every 8h in the UK). Cephalosporins have ~1% cross-reactivity with penicillin in non-anaphylactic allergy.

If anaphylactic (angioedema, anaphylaxis, urticaria, bronchospasm):

• I would test GBS isolate for clindamycin susceptibility (should be done at time of screening if high-risk allergy documented).
• If sensitive: Clindamycin 900mg IV every 8 hours.
• If resistant or unknown: Vancomycin 1g IV every 12 hours.

I would document the allergy clearly, liaise with the anaesthetic and neonatal teams, and ensure the woman has access to emergency treatment for anaphylaxis if needed."

Viva Point: Scenario 2: Inadequate IAP and Neonatal Management

Examiner: "A woman with positive GBS culture delivered vaginally 1 hour after receiving benzylpenicillin. The baby appears well. What is your neonatal management plan?"

Model Answer: "The neonate received inadequate IAP (less than 4 hours, specifically only 1 hour), which provides limited protection against GBS transmission.

My approach would be:

1. Enhanced observation for minimum 24 hours in hospital.
2. Clinical monitoring: Temperature (every 3 hours), respiratory rate, feeding, activity, color.
3. Baseline investigations: I would consider FBC and CRP (although CRP may be falsely reassuring in first 12 hours). Some centers use the neonatal sepsis calculator to individualize risk.
4. Repeat CRP at 24 hours if initial concerns or if clinical deterioration.
5. Low threshold for antibiotics: If ANY clinical signs develop (respiratory distress, lethargy, poor feeding, temperature instability), perform full septic screen (blood culture, FBC, CRP, LP if stable, CXR if respiratory signs) and start empirical antibiotics (benzylpenicillin + gentamicin).
6. Parental education: Advise parents on warning signs and ensure they know how to seek urgent help.

I would document the plan clearly and liaise with neonatal team to ensure appropriate follow-up."

Viva Point: Scenario 3: GBS Meningitis Prognosis Discussion

Examiner: "Parents ask about the long-term prognosis for their neonate with confirmed GBS meningitis. What do you tell them?"

Model Answer: "I would approach this sensitively, acknowledging their anxiety. I would explain:

'GBS meningitis is a serious infection, but with prompt treatment, most babies survive. However, I need to be honest that there is a risk of long-term effects.

Survival: With treatment, about 90-95% of babies survive GBS meningitis.

Long-term outcomes: Among survivors, approximately 20-30% may have some degree of neurological problems. These can include:

• Developmental delay (slower to reach milestones, learning difficulties)
• Cerebral palsy (affecting movement and coordination)
• Hearing loss (which is why we will do hearing tests)
• Seizures (epilepsy)
• Hydrocephalus (fluid on the brain, which may require a shunt)

The majority (70-80%) of survivors develop normally without long-term problems.

We cannot predict at this stage which babies will have long-term effects, so we will:

• Give 14-21 days of IV antibiotics to ensure complete treatment.
• Perform a repeat lumbar puncture after 48 hours to check the infection is clearing.
• Arrange MRI brain scan to assess any brain injury.
• Perform hearing tests (before discharge and again at 6 months).
• Organize neurodevelopmental follow-up at 6 months, 12 months, and 2 years to monitor development and provide early intervention if needed.

I know this is a lot to take in, and we are here to support you throughout.'"

Common Mistakes to Avoid

Exam Detail: ❌ Mistake 1: Stating that UK uses universal GBS screening (INCORRECT – UK uses risk-based approach). [7]

❌ Mistake 2: Giving IAP for planned elective caesarean section before labour and membrane rupture (NOT required). [5,7]

❌ Mistake 3: Saying IAP prevents late-onset disease (INCORRECT – IAP only prevents EOD). [4]

❌ Mistake 4: Forgetting to ask about the type of penicillin allergy before choosing alternative antibiotic. Anaphylactic allergy requires different management (vancomycin or clindamycin, NOT cephalosporin). [5]

❌ Mistake 5: Not mentioning lumbar puncture in the management of confirmed neonatal GBS sepsis (essential to exclude/confirm meningitis, as it changes antibiotic duration). [14]

❌ Mistake 6: Stating that screening is done at "36 weeks" when ACOG specifies 36 0/7 to 37 6/7 weeks (precise timing matters for exam answers). [5]

---

13. Patient/Layperson Explanation

What is Group B Strep (GBS)?

Group B Streptococcus, or GBS, is a type of bacteria that lives harmlessly in the gut and vagina of about 1 in 5 women. It usually causes no problems for you as an adult.

Why Does It Matter in Pregnancy?

Although GBS is harmless to most pregnant women, it can occasionally be passed to your baby during labour and birth. In rare cases (about 1 in 2000 births in the UK), this can cause a serious infection in your newborn called "early-onset sepsis." This infection can affect your baby's blood, lungs, or brain.

How is GBS Managed in the UK?

In the UK, we do not routinely test all pregnant women for GBS. Instead, we offer antibiotics during labour (via a drip in your arm) if you have certain risk factors:

• You had a previous baby affected by GBS infection
• GBS was found in your urine during this pregnancy
• GBS was found on a swab (taken for another reason)
• You go into labour before 37 weeks (preterm)
• Your waters break more than 18 hours before your baby is born
• You develop a fever (≥38°C) during labour

If you are having a planned caesarean section before labour starts, you do not need antibiotics for GBS.

What Antibiotics Are Given?

The antibiotics are given through a drip in your arm during labour. The most common antibiotic is called penicillin. If you are allergic to penicillin, we will use a different antibiotic that is safe for you.

The antibiotics are most effective if given at least 4 hours before your baby is born, but even if there is less time, they still provide some protection.

What About My Baby After Birth?

After birth, your baby will be observed carefully for 12-24 hours in the hospital to watch for any signs of infection, such as:

• Difficulty breathing
• Not feeding well
• Being very sleepy or floppy
• Having a fever or being too cold

If your baby shows any of these signs, doctors will do some tests (blood tests, possibly a lumbar puncture) and may start antibiotics immediately. Most babies are absolutely fine and do not develop an infection.

Can GBS Be Prevented?

The antibiotics given during labour significantly reduce the risk of your baby becoming infected. Research shows they reduce the risk by about 80-90%.

In the future, a vaccine may be available that can protect babies from GBS without needing antibiotics during labour. This is currently being developed and tested.

What if I Want to Be Tested for GBS?

In the UK, routine testing is not currently recommended by the NHS because the evidence shows that the risk-based approach (giving antibiotics to women with risk factors) is effective. However, if you have concerns, you can discuss this with your midwife or doctor. Private testing is available if you wish to know your GBS status (a swab test at around 35-37 weeks of pregnancy).

Key Takeaway

GBS is common and usually harmless to you. While it can rarely cause serious infection in newborns, the risk is low, and we have effective ways to protect your baby by giving antibiotics during labour if needed. Your healthcare team will monitor you and your baby carefully to ensure the best outcome.

---

14. References

1. Manuel G, Twentyman J, Noble K, et al. Group B streptococcal infections in pregnancy and early life. Clin Microbiol Rev. 2025;38(1):e0015422. doi:10.1128/cmr.00154-22

2. Russell NJ, Seale AC, O'Driscoll M, et al. Maternal Colonization With Group B Streptococcus and Serotype Distribution Worldwide: Systematic Review and Meta-analyses. Clin Infect Dis. 2017;65(suppl_2):S100-S111. doi:10.1093/cid/cix658

3. Flannery DD, Ramachandran V, Schrag SJ. Neonatal Early-Onset Sepsis: Epidemiology, Microbiology, and Controversies in Practice. Clin Perinatol. 2025;52(1):15-31. doi:10.1016/j.clp.2024.10.002

4. Morgan JA, Zafar N, Cooper DB. Group B Streptococcus and Pregnancy. In: StatPearls. StatPearls Publishing; 2025. PMID:29494050

5. American College of Obstetricians and Gynecologists. Prevention of Group B Streptococcal Early-Onset Disease in Newborns: ACOG Committee Opinion, Number 797. Obstet Gynecol. 2020;135(2):e51-e72. doi:10.1097/AOG.0000000000003668

6. Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Maternal Group B Streptococcus in pregnancy: screening and management (C-Obs 19). 2016.

7. Royal College of Obstetricians and Gynaecologists. Prevention of Early-Onset Neonatal Group B Streptococcal Disease: Green-top Guideline No. 36. 2017. Available at: https://www.rcog.org.uk

8. Hughes RG, Brocklehurst P, Steer PJ, Heath P, Stenson BM. Prevention of early-onset neonatal group B streptococcal disease: Green-top Guideline No. 36. BJOG. 2017;124(12):e280-e305. doi:10.1111/1471-0528.14821

9. Seedat F, Stinton C, Patterson J, et al. Adverse events in women and children who have received intrapartum antibiotic prophylaxis treatment: a systematic review. BMC Pregnancy Childbirth. 2017;17(1):247. doi:10.1186/s12884-017-1432-3

10. Valkenburg-van den Berg AW, Houtman-Roelofsen RL, Oostvogel PM, Dekker FW, Dörr PJ, Sprij AJ. Timing of group B streptococcus screening in pregnancy: a systematic review. Gynecol Obstet Invest. 2010;69(3):174-183. doi:10.1159/000265942

11. Benitz WE, Gould JB, Druzin ML. Antimicrobial prevention of early-onset group B streptococcal sepsis: estimates of risk reduction based on a critical literature review. Pediatrics. 1999;103(6):e78. doi:10.1542/peds.103.6.e78

12. Lohrmann F, Efstratiou A, Sorensen UBS, et al. Maternal Streptococcus agalactiae colonization in Europe: data from the multi-center DEVANI study. Infection. 2025;53(1):373-381. doi:10.1007/s15010-024-02380-0

13. Shane AL, Sánchez PJ, Stoll BJ. Neonatal sepsis. Lancet. 2017;390(10104):1770-1780. doi:10.1016/S0140-6736(17)31002-4

14. Tavares T, Pinho L, Bonifacio Andrade E. Group B Streptococcal Neonatal Meningitis. Clin Microbiol Rev. 2022;35(2):e0007921. doi:10.1128/cmr.00079-21

15. Kessous R, Weintraub AY, Sergienko R, et al. Bacteruria with group-B streptococcus: is it a risk factor for adverse pregnancy outcomes? J Matern Fetal Neonatal Med. 2012;25(10):1983-1986. doi:10.3109/14767058.2012.671871

16. Tita AT, Andrews WW. Diagnosis and management of clinical chorioamnionitis. Clin Perinatol. 2010;37(2):339-354. doi:10.1016/j.clp.2010.02.003

17. Teatero S, Athey TB, Van Caeseele P, et al. Emergence of serotype IV group B Streptococcus adult invasive disease in Manitoba and Saskatchewan, Canada, is driven by clonal sequence type 459 strains. J Clin Microbiol. 2015;53(9):2919-2926. doi:10.1128/JCM.01128-15

18. Furfaro LL, Chang BJ, Payne MS. Perinatal Streptococcus agalactiae Epidemiology and Surveillance Targets. Clin Microbiol Rev. 2018;31(4):e00049-18. doi:10.1128/CMR.00049-18

19. Yancey MK, Duff P, Kubilis P, Clark P, Frentzen BH. Risk factors for neonatal sepsis. Obstet Gynecol. 1996;87(2):188-194. doi:10.1016/0029-7844(95)00402-5

20. Le Doare K, Kampmann B. Breast milk and Group B streptococcal infection: vector of transmission or vehicle for protection? Vaccine. 2014;32(26):3128-3132. doi:10.1016/j.vaccine.2014.04.020

21. Baker CJ, Carey VJ, Rench MA, et al. Maternal antibody at delivery protects neonates from early onset group B streptococcal disease. J Infect Dis. 2014;209(5):781-788. doi:10.1093/infdis/jit549

22. Royal College of Obstetricians and Gynaecologists. Preterm Prelabour Rupture of Membranes: Green-top Guideline No. 44. 2019.

23. Valkenburg-van den Berg AW, Sprij AJ, Oostvogel PM, et al. Prevalence of colonisation with group B Streptococci in pregnant women of a multi-ethnic population in The Netherlands. Eur J Obstet Gynecol Reprod Biol. 2006;124(2):178-183. doi:10.1016/j.ejogrb.2005.06.007

24. El Helali N, Nguyen JC, Ly A, Giovangrandi Y, Trinquart L. Diagnostic accuracy of a rapid real-time polymerase chain reaction assay for universal intrapartum group B streptococcus screening. Clin Infect Dis. 2009;49(3):417-423. doi:10.1086/600303

25. National Institute for Health and Care Excellence. Neonatal infection: antibiotics for prevention and treatment (NG195). 2021. Available at: https://www.nice.org.uk/guidance/ng195

26. Kuzniewicz MW, Escobar GJ, Forquer H, et al. Update to the Neonatal Early-Onset Sepsis Calculator Utilizing a Contemporary Cohort. Pediatrics. 2024;154(4):e2023065267. doi:10.1542/peds.2023-065267

27. De Cueto M, Sanchez MJ, Sampedro A, Miranda JA, Herruzo AJ, Rosa-Fraile M. Timing of intrapartum ampicillin and prevention of vertical transmission of group B streptococcus. Obstet Gynecol. 1998;91(1):112-114. doi:10.1016/s0029-7844(97)00587-x

28. Heyderman RS, Madhi SA, French N, et al. Group B streptococcus vaccination in pregnant women with or without HIV in Africa: a non-randomised phase 2, open-label, multicentre trial. Lancet Infect Dis. 2016;16(5):546-555. doi:10.1016/S1473-3099(15)00484-3

29. Ho M, Chang YY, Chang WC, et al. Oral Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 to reduce Group B Streptococcus colonization in pregnant women: A randomized controlled trial. Taiwan J Obstet Gynecol. 2016;55(4):515-518. doi:10.1016/j.tjog.2016.06.003

30. Castor ML, Whitney CG, Como-Sabetti K, et al. Antibiotic resistance patterns in invasive group B streptococcal isolates. Infect Dis Obstet Gynecol. 2008;2008:727505. doi:10.1155/2008/727505

31. Stearns JC, Simioni J, Gunn E, et al. Intrapartum antibiotics for GBS prophylaxis alter colonization patterns in the early infant gut microbiome of low risk infants. Sci Rep. 2017;7:16527. doi:10.1038/s41598-017-16606-9

32. Schrag SJ, Zywicki S, Farley MM, et al. Group B streptococcal disease in the era of intrapartum antibiotic prophylaxis. N Engl J Med. 2000;342(1):15-20. doi:10.1056/NEJM200001063420103

---