Group B Streptococcus Vaginal Colonization Guidelines

Understanding GBS Colonization

Approximately 10-30% of all women are colonized with GBS in the vagina or rectum, and most women have no symptoms associated with this colonization, according to the Centers for Disease Control and Prevention 1, 2, 3
The gastrointestinal tract is the natural reservoir for GBS, and vaginal colonization occurs through spread from this primary source, as stated by the Centers for Disease Control and Prevention 1, 2
Colonization is typically asymptomatic—most women with GBS in the vagina have no symptoms whatsoever, as reported by the Centers for Disease Control and Prevention 1, 2
Colonization patterns vary: GBS can be transient, chronic, or intermittent, meaning it may come and go over time, according to the Centers for Disease Control and Prevention 2, 3

Pregnant women with GBS colonization are more than 25 times more likely to deliver infants with early-onset GBS disease compared to non-colonized women, as stated by the Centers for Disease Control and Prevention 2, 3
However, only 1-2% of infants born to colonized mothers actually develop invasive GBS disease without intervention, according to the Centers for Disease Control and Prevention 3
The American College of Obstetricians and Gynecologists recommends that pregnant women with GBS colonization should receive intrapartum antibiotic prophylaxis to reduce the risk of neonatal infection, as supported by evidence from the Centers for Disease Control and Prevention 2, 3

If GBS is found in urine during pregnancy at any concentration, this indicates heavy colonization and requires intrapartum antibiotic prophylaxis regardless of colony count, as recommended by the American College of Obstetricians and Gynecologists 4, 5
GBS bacteriuria complicates 2-4% of pregnancies and is considered a surrogate marker for heavy maternal colonization and higher risk for neonatal disease, according to the Centers for Disease Control and Prevention 1, 4, 5, 6, 3

For non-pregnant women, GBS vaginal colonization requires no treatment, as stated by the Centers for Disease Control and Prevention 1, 2, 3, 4
Treatment is only indicated if there are symptomatic urinary tract infections or other invasive infections, according to the Infectious Diseases Society of America 4

Antimicrobial agents should not be used before the intrapartum period to treat asymptomatic GBS colonization, as recommended by the Centers for Disease Control and Prevention 2
Colonization status can change between treatment and delivery, making prenatal treatment ineffective, according to the Centers for Disease Control and Prevention 2, 3