FFinalistSouthampton · 2027
Obstetrics & gynaecology
AKT · Obstetrics & gynaecology/Late pregnancy & labour

Group B Streptococcus in pregnancy

Streptococcus agalactiae — maternal genital/rectal coloniser

Overview

GBS colonises the vagina/rectum of ~20–25% of women and is the leading cause of EARLY-ONSET neonatal sepsis. The UK uses a RISK-BASED intrapartum antibiotic prophylaxis (IAP) strategy — it does NOT offer universal antenatal screening (unlike the USA).

Recognise

  • Usually asymptomatic maternal colonisation (often an incidental swab/urine finding)
  • Risk of vertical transmission in labour → early-onset neonatal GBS sepsis/pneumonia/meningitis (<7 days)
  • GBS bacteriuria in pregnancy = heavier colonisation → treat + IAP in labour

Red flags

  • Preterm labour, intrapartum pyrexia ≥38°C / suspected chorioamnionitis, prolonged rupture of membranes, or a previous baby with GBS disease → offer IAP

Differentials & how to tell them apart

Chorioamnionitismaternal fever + uterine tenderness + fetal tachycardia → broad-spectrum IV antibiotics + expedite delivery (not just GBS prophylaxis)
Other causes of neonatal sepsis (E. coli, Listeria)covered by neonatal sepsis pathway/screen
UTI in pregnancysymptomatic; GBS bacteriuria may be incidental

Investigations

No universal screening in the UK. GBS found incidentally on a vaginal/rectal swab or in urine. Decision to give IAP is based on RISK FACTORS, not a screening result.

Management

Intrapartum IV benzylpenicillin as soon as labour starts (risk-based IAP)

  1. 1Offer intrapartum antibiotic prophylaxis (IV benzylpenicillin) to women with risk factors: previous infant with GBS disease, GBS in this pregnancy, preterm labour, pyrexia ≥38°C, or prolonged ROM.Gate: Penicillin allergy → cefuroxime; severe allergy/anaphylaxis → vancomycin
  2. 2Suspected chorioamnionitis → broad-spectrum IV antibiotics AND expedite delivery (IAP alone is not enough).
  3. 3Previous baby affected → IAP regardless of swab status (and discuss in this pregnancy).
Benzylpenicillin IV — first-line intrapartum prophylaxis — as soon as possible in labour, ideally ≥4h before birth
Cefuroxime / vancomycin — penicillin allergy (vancomycin if severe/anaphylaxis)

Key points

The exam contrast: the UK is RISK-BASED (no routine screening); the US screens universally at 35–37 weeks. IAP prevents EARLY-onset (not late-onset) neonatal GBS disease.

Monitor & prognosis

Observe the neonate per the early-onset sepsis pathway if risk factors/inadequate IAP.

IAP markedly reduces early-onset neonatal GBS sepsis.

Source: RCOG Green-top Guideline 36 (GBS in pregnancy)