Prevention of neonatal Group B streptococcal infections

Group B streptococcus (GBS) infections are caused by Streptococcus agalactiae and are the leading cause of neonatal sepsis. Early-onset GBS infection occurs within the first 6 days of life and is typically due to vertical transmission. Late-onset GBS infection occurs between 7 and 89 days of life and is more commonly due to horizontal transmission. Prevention methods target both the pregnant individual and the newborn. Universal prenatal GBS screening and targeted intrapartum GBS prophylaxis have decreased vertical transmission and significantly reduced rates of early-onset GBS infections. In addition, all newborns undergo a neonatal GBS risk assessment shortly after birth to identify individuals who would benefit from early interventions (e.g., close observation, diagnostic evaluation, and/or empiric antibiotics) for early-onset GBS infection.

Classification of GBS infection in infants ^[1][2][3]

• Early-onset GBS infection
  • Confirmed S. agalactiae infection that occurs between birth and 6 days of life ^[1][2]
  • Typically acquired vertically from the birthing parent during labor or delivery
  • Includes neonatal sepsis, neonatal meningitis, and neonatal pneumonia ^[4]
• Late-onset GBS infection
  • Confirmed S. agalactiae infection that occurs between 7 and 89 days of life ^[1]
  • Typically acquired horizontally from nosocomial or community environments
  • Includes bacteremia, neonatal meningitis, neonatal pneumonia, skin and soft tissue infections, osteomyelitis, and septic arthritis ^[4]
• Very late-onset GBS infection
  • Confirmed S. agalactiae infection that occurs after ≥ 90 days of life ^[1]
  • Primarily occurs in infants born very preterm or with immunodeficiency

The cutoff used to define early-onset GBS infection (i.e., < 7 days) differs from the cutoff most commonly used to define early-onset neonatal sepsis (i.e., < 72 hours). ^[1][5]

Risk factors for early-onset GBS infection ^[1][2][5]

• Maternal GBS colonization (e.g., high rectovaginal counts, bacteriuria)
• Maternal intrapartum temperature ≥ 38.0 °C (100.4 °F) ^[2]
• Intra-amniotic infection
• Prolonged rupture of membranes lasting ≥ 18 hours
• Previous newborn affected with GBS
• Preterm birth
• Very low birth weight

Maternal colonization with GBS is the most significant risk factor for early-onset neonatal GBS infections. ^[1][2]

Approach to prevention of GBS infection in infants ^[1][2][5]

• Perform universal prenatal GBS screening.
• Administer intrapartum GBS prophylaxis in pregnant individuals with indications.
• Perform a standardized assessment of all newborns for GBS risk factors to identify indications for further diagnostic testing and/or antibiotic treatment. ^[1]

There is no proven prevention strategy for late-onset GBS infection. ^[1][5]

This section focuses on preventive measures for neonatal GBS infection administered to asymptomatic pregnant individuals during the intrapartum period. For management of GBS-related maternal infections, see “Chorioamnionitis,” “Endometritis,” “Postpartum endometritis,” “Urinary tract infection in pregnancy,” and “Postpartum mastitis.”

Indications ^[1][2][6]

GBS prophylaxis is indicated at the onset of labor and/or rupture of membranes in pregnant individuals with any of the following:

• History of early-onset GBS infection in a previous newborn
• Confirmed GBS colonization during the current pregnancy, i.e.:
  • Positive GBS culture
  • GBS bacteriuria (regardless of colony count)
• Unknown GBS culture result in the current pregnancy and any of the following: ^[1][2]
  • Imminent preterm delivery < 37+0 weeks' gestation or PPROM
  • Prolonged rupture of membranes lasting ≥ 18 hours
  • Maternal intrapartum temperature ≥ 38.0 °C (100.4 °F)
  • Positive intrapartum GBS NAAT
  • Positive GBS culture or GBS bacteriuria in a previous pregnancy ^[2]

Regardless of GBS culture results, intrapartum GBS prophylaxis is not needed if cesarean delivery is performed before the onset of labor and membranes remain intact. ^[2]

Antibiotic regimens ^[1][2]

If indicated, start antibiotic prophylaxis ideally ≥ 4 hours before delivery.

• No penicillin allergy: Start one of the following IV beta-lactam antibiotics.
  • Preferred: penicillin G (off-label) ^[1][2]
  • Alternative: ampicillin (off-label) ^[1][2]
• Penicillin allergy
  • Low risk penicillin allergy: cefazolin (off-label) ^[1][2]
  • Severe penicillin allergy
    • Clindamycin-susceptible GBS: clindamycin (off-label) ^[1][2]
    • Clindamycin-resistant GBS or unknown clindamycin susceptibility: vancomycin (off-label) ^[1][2]

Do not delay any necessary obstetric interventions just to administer ≥ 4 hours of GBS prophylaxis. ^[2]

If the severity of penicillin allergy is unclear, consider penicillin allergy testing during pregnancy to guide GBS prophylaxis at delivery. ^[1][2]

GBS prophylaxis considerations in preterm labor ^[2]

• Manage patients in consultation with an obstetrician.
• Start intrapartum prophylactic antibiotics for GBS.
• If GBS status is unknown, obtain GBS culture and NAAT prior to starting antibiotics.
• If preterm labor is arrested, GBS prophylaxis may be discontinued.
• If previously arrested preterm labor resumes:
  • Review prior GBS culture results to determine if there are indications for GBS prophylaxis.
  • For negative GBS culture results, repeat GBS NAAT and culture if ≥ 5 weeks since the prior result.

This section outlines the immediate postdelivery measures for all newborns born at ≥ 35 weeks' gestation.

Approach ^[1][5]

• Perform a GBS risk assessment on all newborns to guide management options, e.g.:
  • Routine newborn care
  • Close observation with serial physical examinations and vital signs for 36–48 hours ^[1][5]
  • Blood cultures with or without empiric antibiotics
• If empiric antibiotics are recommended:
  • Start treatment and consult or transfer to the NICU.
  • Consider obtaining CSF culture before starting antibiotics, especially for severe illness and/or a positive blood culture.
  • Narrow or discontinue antibiotics if all of the following are met:
    • Cultures are negative at 36–48 hours ^[5]
    • No signs of site-specific infection
    • No critical unexplained illness
  • If cultures are positive, provide management for neonatal bacterial infection.

CBC and inflammatory markers are not reliable predictors of early-onset GBS infection. ^[1][5]

Risk assessment and management ^[1][5]

Different methods may be used to guide management based on the presence of risk factors for early-onset GBS infection and/or clinical features of neonatal infection.

• Categorical risk factor assessment: uses predefined risk factor thresholds to guide management
  • Maternal intrapartum temperature ≥ 38.0 °C (100.4 °F) and/or clinical signs of neonatal infection: blood cultures and empiric antibiotics ^[1]
  • Inadequate maternal GBS prophylaxis: clinical observation for 36–48 hours ^[1]
  • None of the above: routine newborn care
• Multivariate risk assessment ^[7][8][9]
  • An individualized risk score is calculated using multiple variables, e.g.:
    • Maternal and neonatal factors
    • Type and length of intrapartum antibiotics
    • Local incidence of early-onset sepsis
    • Clinical evaluation
  • Risk score is used to guide management.
  • See “Tips and links” for the “Neonatal early-onset calculator.”
• Enhanced observation: relies on clinical evaluation to detect signs of illness and guide management
  • Clinical signs of neonatal infection: blood cultures and empiric antibiotics
  • Maternal intrapartum temperature ≥ 38.0 °C (100.4 °F) or inadequate maternal GBS prophylaxis: serial physical examination with vital signs for 36–48 hours ^[1]
  • None of the above: routine newborn care

Adequate maternal GBS prophylaxis is defined as ≥ 4 hours of penicillin G, ampicillin, or cefazolin before delivery. Neonatal risk assessments do not consider clindamycin or vancomycin to be adequate preventive treatment. ^[1] Infants can still develop early-onset GBS infection even if their birthing parent screened negative for GBS. ^[1]

Empiric antibiotics for early-onset GBS infection ^[1][4][5]

• Ampicillin ^[4]
• PLUS an aminoglycoside (e.g., gentamicin ) ^[4]