Perinatal infections I: group B streptococcus

A 30-year-old woman at 38 weeks gestation presents in spontaneous labour at 4 cm dilatation. Her GBS swab at 36 weeks was positive. The registrar's question — when to start the antibiotic, what dose, what agent — is the question this topic rehearses. The decisions — screening approach, IAP regimen, allergy alternatives, neonatal communication — are the decisions that prevent neonatal sepsis.[1][2]

Overview and definition

Group B streptococcus (GBS, Streptococcus agalactiae) is a Gram-positive encapsulated bacterium that colonises the maternal gastrointestinal and genitourinary tracts in roughly 10 to 30 per cent of women. It is the leading cause of neonatal sepsis in high-income settings.[1][5]

Two clinical entities matter for the candidate:[1][7]

• Early-onset GBS disease (EOGBSD) — sepsis, pneumonia or meningitis in the first 7 days of life, acquired through vertical transmission at birth. The target of antenatal screening and intrapartum antibiotic prophylaxis.
• Late-onset GBS disease (LOGBSD) — presenting from day 7 to day 89, often with meningitis. Not preventable by intrapartum antibiotic prophylaxis, and the focus of ongoing vaccine development.[7][8]

Two principles frame the topic. First, antenatal screening and intrapartum antibiotic prophylaxis prevent early-onset disease but not late-onset disease. Second, the choice of antibiotic and the timing of administration matter — the regimen must achieve adequate fetal and amniotic fluid concentrations at least 4 hours before delivery.[1][11]

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1. [1]American College of Obstetricians and Gynecologists' Committee on Obstetric Practice Prevention of Group B Streptococcal Early-Onset Disease in Newborns: ACOG Committee Opinion, Number 797 Obstet Gynecol, 2020.PMID 31977795
2. [2]Ohlsson A, Shah VS Intrapartum antibiotics for known maternal Group B streptococcal colonization Cochrane Database Syst Rev, 2014.PMID 24915629
3. [3]Schrag SJ, Verani JR Intrapartum antibiotic prophylaxis for the prevention of perinatal group B streptococcal disease: experience in the United States and implications for a potential group B streptococcal vaccine Vaccine, 2013.PMID 23219695
4. [4]Verani JR, McGee L, Schrag SJ, et al. Prevention of perinatal group B streptococcal disease--revised guidelines from CDC, 2010 MMWR Recomm Rep, 2010.PMID 21088663
5. [5]Seale AC, Bianchi-Jassir F, Russell NJ, et al. Estimates of the Burden of Group B Streptococcal Disease Worldwide for Pregnant Women, Stillbirths, and Children Clin Infect Dis, 2017.PMID 29117332
6. [6]Kohli-Lynch M, Russell NJ, Seale AC, et al. Neurodevelopmental Impairment in Children After Group B Streptococcal Disease Worldwide: Systematic Review and Meta-analyses Clin Infect Dis, 2017.PMID 29117331
7. [7]Nanduri SA, Petit S, Smelser C, et al. Epidemiology of Invasive Early-Onset and Late-Onset Group B Streptococcal Disease in the United States, 2006 to 2015: Multistate Laboratory and Population-Based Surveillance JAMA Pediatr, 2019.PMID 30640366
8. [8]Edwards MS, Baker CJ Group B Streptococcal Disease: Interim Prevention at 50 Years and Counting Clin Infect Dis, 2020.PMID 31394571
9. [9]El Helali N, Giovangrandi Y, Guyot K, et al. Cost and effectiveness of intrapartum group B streptococcus polymerase chain reaction screening for term deliveries Obstet Gynecol, 2012.PMID 22433346
10. [10]El Helali N, Habibi F, Azria E, et al. Point-of-Care Intrapartum Group B Streptococcus Molecular Screening: Effectiveness and Costs Obstet Gynecol, 2019.PMID 30633130
11. [11]Deegan B, Gourlay A, Eriksson L, et al. Benzylpenicillin Concentrations in Intrapartum Group B Streptococcus Prevention Guidelines; A Systematic Review of the Evidence Aust N Z J Obstet Gynaecol, 2026.PMID 42381244
12. [12]Benitz WE Perinatal treatment to prevent early onset group B streptococcal sepsis Semin Neonatol, 2002.PMID 12401300
13. [13]Horváth-Puhó E, van Kassel MN, Gonçalves BP, et al. Mortality, neurodevelopmental impairments, and economic outcomes after invasive group B streptococcal disease in early infancy in Denmark and the Netherlands: a matched cohort study Lancet Child Adolesc Health, 2021.PMID 33894156
14. [14]Saunders M, Ojha S, Szatkowski L Impact of NICE clinical guidelines for prevention and treatment of neonatal infections on antibiotic use in very preterm infants in England and Wales: an interrupted time series analysis. Arch Dis Child Fetal Neonatal Ed, 2024.PMID 38802167