What Is Group B Strep?

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Group B Streptococcus (group B strep or GBS) is a bacterium that occurs naturally in the gastrointestinal and genital tracts (vagina, uterus, and fallopian tubes). Since it lives in the vagina and rectum of some people, GBS can be passed from the pregnant parent to the baby during labor.

Although the bacterium is not usually harmful to adults, it can cause serious side effects in infants. People who are positive for GBS will need to be treated with antibiotics during labor to help prevent the baby from being infected.

This article will discuss the cause, symptoms, risk factors, complications, and prevention of group B strep.

Pregnant person and doctor

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Bacteria are microscopic, single-celled organisms that live in the environment. For example, Streptococcus (strep) is a type of bacteria found inside and outside humans and animals. Not to be confused with group A strep, which is responsible for strep throat, group B strep is sometimes found in the rectum and vagina of people.

Although GBS may be spread through sexual contact, it is not considered a sexually transmitted infection (STI). GBS affects approximately 25% of those who are pregnant. The bacterium infects the fetus as it passes through the birth canal. If untreated, a baby born to a GBS-positive person is 20 times more likely to develop GBS.

Types of Streptococcus

There are four types of streptococcus: groups A, B, C, and G. Groups C and G are rare, affecting animals such as horses and cattle. Humans can contract strep C and G by drinking raw milk or contacting infected animals.

Signs and Symptoms

Symptoms of GBS depend on the body part that's infected with the bacterium. For example, cystitis (bladder pain) or pyelonephritis (kidney infection) can occur if the urinary tract is infected with GBS.

Bacteria can travel to other organs like the lungs or brain if they enter the bloodstream. GBS can also affect the bones, joints, and soft tissue. After birth, newborns who acquire GBS can become very sick with meningitis (brain infection).

Common symptoms of GBS in adults include:

  • Fever
  • Chills
  • Feeling poorly
  • Confusion
  • Pain, frequency, and burning upon urination
  • Bone pain
  • Tissue swelling, warmth, and pain

Common symptoms of GBS in newborns include:

  • Poor eating
  • Fever
  • Lethargy or irritability
  • Difficulty breathing
  • Low body temperature
  • Seizures

If you were treated for GBS during labor and your baby begins to show signs of GBS infection, seek medical attention immediately.

Risk Factors

Adults at high risk for GBS infection include those who have the following:

Since pregnant people are tested for GBS between 36 and 37 weeks' gestation, a baby born prematurely—before this time frame—is at risk of developing GBS disease. Other risk factors for infants include:

  • The birthing parent experiences ruptured membranes for 18 or more hours before delivery.
  • The birthing parent has a fever during labor.
  • The birthing parent currently has or has had a urinary tract infection (UTI) during pregnancy.
  • An infection of the placenta or amniotic fluid occurs.
  • Antibiotics were not received due to a precipitous (fast) labor.


Most pregnant people with GBS are not symptomatic; they likely don't know they have the bacterium. However, complications of GBS in adults are septicemia (blood infection), heart infection, pneumonia, skin infections, bone/joint infections, and meningitis.

Infants showing signs of infection within 12 hours to seven days after birth have early-onset GBS disease. Meningitis, pneumonia, and septicemia are grave complications of early onset GBS. Side effects from meningitis include deafness and long-term developmental disabilities. Unfortunately, 4%–5% of babies with GBS disease will die.

Some infants can become infected with GBS seven days to three months after birth; this is called late-onset GBS disease. These infants can also suffer long-term health issues from meningitis.

Neonatal Meningitis

The meninges are membranes that protect the brain and spinal cord. When these membranes become infected in a newborn it's called neonatal meningitis. A spinal tap is done to diagnose neonatal meningitis.


Although scientists are working on a vaccine, there is no way to prevent GBS in pregnant people. However, the best prevention for infants is for the parent to be tested for GBS during pregnancy.

Diagnosis of GBS can be made by a swab test, a urine test, or blood test. If you test positive for GBS, you will receive intravenous antibiotics during labor. Unfortunately, oral antibiotics are not strong enough to protect the infant from GBS disease safely.

If you have a planned cesarean birth (C-section), antibiotics are not required, as the risk of passing GBS to the infant born by C-section is lower than for vaginal birth. However, you will still need to be tested for GBS in case you go into labor before your scheduled C-section.

You will only be treated for GBS before labor should you become symptomatic of a GBS infection such as a UTI, a skin infection, or pneumonia. Oral antibiotics before labor are not effective in preventing GBS disease in infants.


Group B strep is a type of bacteria typically found in the rectum and vagina of some people, including 25% of pregnant parents. GBS can be spread to the baby during childbirth. If untreated, GBS can result in life-threatening consequences for the infant.

If the birthing parent receives intravenous antibiotics during labor, they will drastically reduce the chance of their newborn being infected with GBS. Although there is no prevention for adults, it's essential for pregnant people to be tested for the bacterium during pregnancy as a vital safety measure for preventing GBS disease in newborns.

A Word From Verywell

GBS testing is part of routine prenatal care, which can start before becoming pregnant. GBS is more prevalent in people who are overweight and diabetic. So, receiving prepregnancy care for these conditions may help reduce your chances of becoming infected with the bacterium. If you have risk factors that make you susceptible to GBS, talk to your pregnancy care provider (such as an obstetrician) about taking precautions for group B strep.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Centers for Disease Control. Group b strep: facts and statistics.

  3. Centers for Disease Control. Diagnosis, treatment and complications of group b strep.

  4. Centers for Disease Control. Signs and symptoms of group b strep.

  5. American College of Obstetricians and Gynecologists. Group b strep and pregnancy.

  6. Davies HG, Carreras-Abad C, Le Doare K, Heath PT. Group b streptococcus: trials and tribulations. Pediatric Infectious Disease Journal. 2019;38(6S):S72-S76. doi: 10.1097/INF.0000000000002328

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By Serenity Mirabito RN, OCN
Serenity Mirabito, MSN, RN, OCN, advocates for well-being, even in the midst of illness. She believes in arming her readers with the most current and trustworthy information leading to fully informed decision making.