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What is Group B strep?

What is Group B strep?

Navin Khosla NowPatientGreen tick
Created on 1 Jul 2024
Updated on 16 Jul 2024

Group B streptococcus or Group B strep, is a common bacterium found in the gastrointestinal and genital tracts of many healthy adults. While it is usually harmless in adults, Group B strep infections can pose serious risks to newborn babies (neonates) during the first week of life if left untreated. Babies’ immune systems are less developed and can not fight off bacteria effectively. As a leading cause of life-threatening infections in newborn babies, understanding the nature, risks, and prevention of GBS is crucial for expecting mothers and healthcare providers.

What is Group B Streptococcus?

Group B Streptococcus (GBS) is a type of bacteria found in the lower intestine, vagina, and rectum of approximately 25% of healthy adult women. It is a common and natural inhabitant of the human body, and in most cases, does not cause any harm. However, GBS can be passed from a pregnant woman to her baby during childbirth, causing serious complications if not properly managed.

Studies estimate that 10-30% of pregnant women have GBS bacteria in their body. The amount of bacteria can vary depending on age, race, and geographic location. Even though the presence of GBS is common, it does not necessarily mean an individual will develop an infection or pass the bacteria on to their newborn.

How is Group B Streptococcus transmitted?

Group B Streptococcal disease can be transmitted from a pregnant woman to her baby during labor and delivery, when the baby comes into contact with the bacteria in the birth canal or amniotic fluid. Certain risk factors increase the likelihood of GBS transmission, including:

  • Preterm birth (before 37 weeks of pregnancy)
  • Prolonged rupture of membranes (water breaking more than 18 hours before delivery)
  • Mother suffering from a fever during labor
  • Previous delivery of a baby with GBS infection
  • Mother with a urinary tract infection caused by GBS

Risks and complications of GBS in newborns

Group B Streptococcal infections in newborns can lead to serious and potentially life-threatening complications, such as:

Early-onset Group B Strep Infections

Early-onset GBS disease typically occur within the first week of a baby’s life, often within the first 24 hours. Symptoms may include fever, difficulty breathing, lethargy, and poor feeding. These infections can cause pneumonia, sepsis, and meningitis (inflammation of the membranes surrounding the brain and spinal cord).

Late-onset Group B Strep Infections

Late-onset GBS disease can develop in babies between one week and three months of age. Symptoms may include fever, poor feeding, irritability, and breathing difficulties. This can lead to serious infections such as sepsis and meningitis and may be acquired from sources other than the mother, such as healthcare providers or other family members.

Long-term consequences

Babies who survive a GBS infection may face long-term health issues, such as hearing loss, vision problems, cerebral palsy, and developmental delays. In severe cases, GBS infections can be fatal, with a mortality rate of around 5-10% for early-onset infections and 2-3% for late-onset infections.

Screening and prevention of GBS

Screening for GBS during pregnancy is a crucial step in preventing infections in newborns. The recommended approach is as follows:

Prenatal GBS Screening

The Centers for Disease Control and Prevention (CDC) recommends that all pregnant women be screened for GBS between week 36 and 37 of pregnancy. This is typically done through a simple vaginal and rectal swab test, which is sent to a laboratory for analysis.

Antibiotic prophylaxis

If a pregnant woman tests positive for GBS, she will be given intravenous antibiotic treatment during labor and delivery. The antibiotic that is offered to prevent GBS infection is usually penicillin. This helps to reduce the risk of passing the bacteria to the baby during the birthing process. Antibiotics are also recommended for women with certain risk factors, even if their GBS status is unknown.

Newborn monitoring and treatment

Newborns of mothers with GBS may be closely monitored for signs of infection and, if necessary, treated with antibiotics. This is particularly important for infants born prematurely or with other risk factors.


While the current screening and prevention strategies have been effective in reducing the rates of GBS infections in newborns, there are still ongoing challenges and research efforts in this area:

Antibiotic resistance

Widespread use of antibiotics during labor and delivery has led to concerns about the development of antibiotic-resistant strains of GBS. Alternative prevention methods, such as GBS vaccines are being developed, to address this issue.

Limitations of screening

The current screening process only detects GBS colonisation at a specific point in time. Some women may test negative during screening but still harbour the bacteria, leading to a potential risk of transmission to their newborns.


Group B Streptococcus can pose serious risks to newborn infants if not properly managed. By understanding the prevalence, transmission, and potential complications of GBS, healthcare professionals and expectant mothers can implement effective screening and prevention strategies.


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NowPatient has taken all reasonable steps to ensure that all material is factually accurate, complete, and current. However, the knowledge and experience of a qualified healthcare professional should always be sought after instead of using the information on this page. Before taking any drug, you should always speak to your doctor or another qualified healthcare provider.

The information provided here about medications is subject to change and is not meant to include all uses, precautions, warnings, directions, drug interactions, allergic reactions, or negative effects. The absence of warnings or other information for a particular medication does not imply that the medication or medication combination is appropriate for all patients or for all possible purposes.

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