Group B Streptococcus: Neonatal Risk, Screening, and Intrapartum Prophylaxis

Overview

Group B streptococcus (GBS) is a beta-hemolytic, Gram-positive bacterium.
It naturally resides in the gastrointestinal, rectal, and genitourinary tracts of healthy adults.
Colonization rate in pregnant individuals can be anywhere from 10\%-30\%.
While often harmless in adults, GBS is the leading cause of neonatal sepsis and meningitis in the United States.
In newborns, the disease is of primary concern; adults are usually asymptomatic carriers or have mild disease.

GBS is a beta-hemolytic Gram-positive bacterium.
It commonly colonizes the gastrointestinal tract, rectum, and genitourinary tract of healthy adults.
Colonization rate in pregnancy: 10\%-30\%.
Reservoirs include the maternal GI, rectal, and GU tracts.
Transmission to the neonate is primarily vertical during labor and delivery (during birth).
Early-onset GBS disease occurs within the first seven days of life, typically manifesting at 24-48\text{ hours} after birth.
Late-onset GBS disease occurs from 7\text{ days} to 3\text{ months} of age.
Early onset is most strongly associated with vertical transmission; late-onset can be vertical but is less common and may be horizontal from the environment or caregivers.
GBS is associated with meningitis and bacteremia in neonates.

Early-onset disease (EOD): occurs within the first seven days of life; typically presents within 24-48\text{ hours}; transmission is usually vertical during labor/delivery.
Symptoms in newborns: respiratory distress, apnea, hypotonia, temperature instability, sepsis, pneumonia, meningitis.
Late-onset disease (LOD): occurs from 7\text{ days} to 3\text{ months} of age; transmission is usually vertical but is the least common; can be horizontal from environment or caregivers.
EOD and LOD are both associated with meningitis and bacteremia.

Universal GBS screening is recommended between 35-37\text{ weeks} gestation via vaginal or rectal swab.
Screening identifies colonization at the time of labor; results are valid for 5\text{ weeks}.
If GBS is detected early in pregnancy, treatment is indicated during labor (intrapartum antibiotic prophylaxis).
It is important to verify GBS status on the labor and delivery record.

IAP is indicated if any of the following are present:
- Positive GBS screening.
- GBS bacteriuria during pregnancy or a previous infant with invasive GBS disease.
- Unknown GBS status.
- One or more risk factors: preterm labor, PROM >18\text{ hours}, or maternal fever during labor.
If the mother had adequate antibiotic therapy during labor: monitor the baby for signs of infection for 48\text{ hours}; no further testing if asymptomatic.
If the mother did not receive adequate antibiotic therapy: monitor the baby closely; consider blood cultures, a CBC, and empiric antibiotics depending on the baby’s condition.

Loading dose: 5{,}000{,}000\text{ units}
Maintenance: 2{,}500{,}000-3{,}000{,}000\text{ units} IV every 4\text{ hours} until delivery
If penicillin allergy and not high risk for anaphylaxis: Cefazolin
If penicillin allergy and GBS susceptible: Clindamycin
If resistance or severe allergy: Vancomycin
Note: If GBS is resistant or there is a severe allergy, adjust antibiotic accordingly (Vancomycin or alternative depending on susceptibility).

For cesarean birth with labor and/or ruptured membranes, intrapartum antibiotics are commonly given.
If cesarean birth is planned and there has been no labor and membranes are intact, intrapartum prophylaxis may not be required.
In practice, most cesarean births involve some antibiotic exposure before delivery regardless.

Ensure timely GBS screening at 35-37\text{ weeks} and verify GBS status in the labor record.
Administer intrapartum antibiotics promptly and appropriately when indicated.
Monitor for and manage allergic reactions to antibiotics during labor.
Monitor for signs of labor or preterm labor that may necessitate intrapartum antibiotics.
Educate patients about the meaning of GBS colonization, the rationale for screening and prophylaxis, and signs of neonatal infection to report after birth.

Vertical transmission during labor is a key concept in perinatal infection control.
Universal screening is a public health approach to prevent severe neonatal disease.
Intrapartum antibiotic prophylaxis is a practical application of antibiotic stewardship to reduce neonatal morbidity.
The management strategy balances maternal autonomy, fetal safety, and resource utilization in prenatal care settings.

Universal screening promotes equity by reducing neonatal sepsis risk across populations, but requires access to prenatal care and follow-through with testing and treatment.
Timely administration of antibiotics must be weighed against potential maternal and neonatal adverse effects and antibiotic resistance considerations.
Education and informed consent are important components of implementing intrapartum prophylaxis in diverse patient populations.

GBS is common and usually harmless in adults but can cause life-threatening neonatal disease if transmitted during birth.
Universal screening at 35-37 weeks and timely intrapartum antibiotic prophylaxis significantly reduce neonatal GBS infection risk.
Nurses play a crucial role in screening verification, timely antibiotic administration, monitoring for adverse reactions, and patient education.