Group B Streptococcus Vaginal Colonization: Normal and Typically Harmless
Yes, it is completely normal and okay to have Group B Streptococcus (GBS) in the vagina—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. 1
Understanding GBS Colonization
GBS colonization is not a sexually transmitted disease and does not require treatment outside of specific circumstances. The key points to understand:
- The gastrointestinal tract is the natural reservoir for GBS, and vaginal colonization occurs through spread from this primary source 1, 2
- Colonization is typically asymptomatic—most women with GBS in the vagina have no symptoms whatsoever 1
- Colonization patterns vary: GBS can be transient, chronic, or intermittent, meaning it may come and go over time 1, 2
- This is not an infection requiring treatment in non-pregnant women or outside of pregnancy-related circumstances 1
When GBS Colonization Matters
During Pregnancy
The primary concern with vaginal GBS colonization is vertical transmission to newborns during delivery, not harm to the mother herself:
- Pregnant women with GBS colonization are >25 times more likely to deliver infants with early-onset GBS disease compared to non-colonized women 1
- However, only 1-2% of infants born to colonized mothers actually develop invasive GBS disease without intervention 1, 3, 4
- Screening is recommended between 36 0/7 and 37 6/7 weeks of gestation to identify women who need intrapartum antibiotic prophylaxis 4, 5
- Intravenous antibiotics during labor reduce neonatal infection risk from approximately 4.7% to 0.4% 3
GBS in Urine
If GBS is found in urine during pregnancy at any concentration, this indicates heavy colonization and requires intrapartum antibiotic prophylaxis regardless of colony count 2, 6:
- GBS bacteriuria complicates 2-4% of pregnancies 1, 2, 6
- This is considered a surrogate marker for heavy maternal colonization and higher risk for neonatal disease 1, 2
Outside of Pregnancy
For non-pregnant women, GBS vaginal colonization requires no treatment:
- Colonization is a normal finding in 10-30% of the adult population 1, 2
- Treatment is only indicated if there are symptomatic urinary tract infections or other invasive infections 2
Important Caveats
Do not attempt to eradicate GBS colonization with antibiotics outside of labor, as:
- Antimicrobial agents should not be used before the intrapartum period to treat asymptomatic GBS colonization 1
- GBS cannot be reliably eradicated by antibiotic treatment outside of labor 7
- Colonization status can change between treatment and delivery, making prenatal treatment ineffective 1
The only exception is GBS urinary tract infection during pregnancy, which should be treated according to standard UTI protocols, though screening cultures at 35-37 weeks are not necessary for these women as they automatically qualify for intrapartum prophylaxis 6.