Published: 18 Jun 2025

ICD9: 041.02      ICD10: B95.1      ICD11: XN2M1

Group B Streptococcus (GBS), also known as Group B Strep or Strep B, is a common type of bacteria that lives in the intestines and/or vagina of about 1 in 4 pregnant women.
It's usually harmless in adults and doesn't cause any symptoms. However, it can be dangerous for newborns.

Here's a breakdown of key aspects of GBS infection:

What it is:

Bacteria: GBS is a type of bacteria, specifically Streptococcus agalactiae.
Colonization, not infection: Many adults are "colonized" with GBS, meaning the bacteria lives on or in their body (usually in the intestines, rectum, or vagina) without causing illness.
Transient: Colonization can come and go. A woman might test positive for GBS at one point in her pregnancy and negative at another.

Risks to Newborns:

Transmission during birth: The biggest concern with GBS is the potential for transmission to a baby during vaginal delivery. Babies can be exposed to the bacteria as they pass through the birth canal.
Early-onset GBS disease: This occurs in the first week of life (usually within 24-48 hours). Symptoms can include:
Sepsis (blood infection)
Pneumonia (lung infection)
Meningitis (infection of the brain and spinal cord)
Breathing problems
Feeding difficulties
Lethargy (lack of energy)
Late-onset GBS disease: This occurs between 1 week and 3 months of age. Symptoms can include:
Meningitis (most common)
Bone or joint infections

How it's Detected During Pregnancy:

Routine screening: Pregnant women are usually screened for GBS between 36 and 37 weeks of gestation.
Swab test: The screening involves taking swabs of the vagina and rectum. These swabs are sent to a lab to see if GBS is present.

Treatment and Prevention:

Antibiotics during labor: If a pregnant woman tests positive for GBS, she will typically be given intravenous (IV) antibiotics during labor (usually penicillin or clindamycin if allergic to penicillin). This greatly reduces the risk of the baby contracting GBS.
No treatment needed if not pregnant: If a woman is not pregnant and tests positive for GBS, treatment is usually not necessary unless she has a specific infection caused by GBS.
No treatment before labor: Antibiotics given before labor are not effective at preventing GBS in the baby because the bacteria can quickly return. The IV antibiotics during labor provide protection right at the time of delivery.
Cesarean section considerations: A scheduled C-section *before* labor begins and *before* the water breaks may eliminate the need for antibiotics because the baby is not exposed to the bacteria in the birth canal. However, C-sections are not routinely performed solely for GBS prevention. If labor has started or membranes have ruptured then IV antibiotics are recommended even if a C-section is performed.

Who Needs Antibiotics During Labor:

Women who test positive for GBS during pregnancy screening.
Women who had a previous baby who developed GBS disease.
Women who develop a fever during labor of unknown origin.
Women whose GBS status is unknown at the time of labor (and who have risk factors such as preterm labor or prolonged rupture of membranes).

Important Considerations:

GBS is not a sexually transmitted infection (STI).
Testing positive for GBS is not a sign of poor hygiene. It's just a common occurrence.
GBS is not dangerous to the mother unless she develops a rare invasive infection, such as a bloodstream infection or a uterine infection after delivery.
Antibiotics during labor are very effective in preventing early-onset GBS disease in newborns. The risk of a baby developing GBS disease is significantly reduced with appropriate antibiotic treatment.

In summary: GBS is a common bacteria that can pose a risk to newborns if transmitted during delivery. Routine screening and antibiotics during labor are highly effective in preventing serious complications. If you are pregnant, talk to your healthcare provider about GBS screening and treatment options. They will assess your individual risk factors and provide personalized recommendations.