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Group B Streptococcal Disease(GBS)

Group B streptococcal (GBS) disease is a bacterial infection.

GBS can cause illness in newborn babies, pregnant women, the elderly, and adults with other chronic medical conditions, such as diabetes or liver disease. In newborns, it is the most common cause of a blood infection called sepsis and of meningitis, which is an infection of the fluid and lining surrounding the brain.

This following information covers GBS in pregnant women and their babies.


GBS disease is caused by specific bacteria. These bacteria live in the gastrointestinal and genital tracts. They are found in the vaginal or rectal areas of 10% to 35% of all healthy adult women. This is called GBS colonization. Only a small number of babies who are exposed to the bacteria will become infected. If infection occurs, it can be serious.

Newborn babies can become infected with GBS in 3 ways:

  • Before birth, bacteria in the vagina can spread up the birth canal into the uterus and infect the amniotic fluid surrounding the fetus. The baby becomes infected by inhaling the infected fluid.
  • During delivery, by contact with bacteria in the birth canal
  • After birth, by close physical contact, usually with the mother

Vaginal Bacteria Spreading to Fetus


Copyright © Nucleus Medical Media, Inc.

Risk Factors

Factors that may increase your baby's chance of GBS include:

  • Mother is GBS positive and does not get antibiotics at least 4 hours before delivery.
  • Mother had a previous baby with GBS disease.
  • Mother has a urinary tract infection due to GBS.
  • Labor or rupture of the membranes before 37 weeks of pregnancy.
  • Rupture of the membranes for 18 hours or more before delivery.
  • Mother has a fever during labor.
  • Frequent vaginal examinations during labor.
  • Use of intrauterine fetal monitoring devices.
  • Mother currently has GBS in the vaginal or rectal area—This is may be confirmed by a lab test between weeks 35-37 of pregnancy.

In pregnant women, GBS infections can sometimes cause inflammation or irritation of the lining of the uterus called endometritis, infection of the uterus and amniotic sac called chorioamnionitis, and loss of pregnancy due to infection.

Symptoms of endometritis and amnionitis may include:

  • Fever
  • Abdominal pain
  • Bad odor of amniotic fluid

Doctors are especially concerned about how GBS infections affect young infants. The disease can occur early in newborns (early-onset) or late (late-onset). Early-onset GBS disease usually causes illness within the first 24 hours of life. However, illness can occur up to 3 days after birth. Late-onset disease usually occurs at 3 to 4 weeks of age. It can occur any time from 4 days to 3 months of age.

Symptoms of GBS include:

  • Unstable temperature—low or high
  • Breathing problems
  • Not eating well
  • Irritability
  • Difficulty waking
  • Weakness or lacking energy—in late-onset disease

GBS colonization can be diagnosed in a pregnant woman at an obstetric office visit. Testing for GBS should be done about one month before the baby is due. The doctor swabs the vagina and rectum and sends this sample to a laboratory to test for GBS. Test results are available in 24-48 hours. Treatment usually does not begin until labor starts.

Your baby's bodily fluids may be tested. This can be done with:

  • Blood tests
  • Culture tests
  • Urine tests
  • Spinal fluid test
For the Mother

If you test positive for GBS or are at high risk, your doctor will recommend giving you antibiotics through an IV during labor and delivery. Antibiotics will reduce the risk that your baby will get sick after birth if given at least 4 hours before delivery. Even with screening and antibiotic treatment, some babies can still get GBS.

It is generally not recommended that women take antibiotics before labor to prevent GBS unless GBS is identified in the urine. It is not as effective at preventing illness unless it is given after labor has begun.

For the Baby

If the doctor suspects strep B infection, a newborn might be kept in the hospital a couple of extra days for monitoring, which will include blood and urine tests. A baby diagnosed with GBS will be treated with IV antibiotics for 10 days. If GBS is suspected, antibiotics may be started before a diagnosis is made. Seek medical care right away if your baby has any of the symptoms of GBS infection.


Methods to prevent GBS may include:

  • Screening pregnant women at 35-37 weeks—If GBS is found through the screening, IV antibiotics are given during labor and delivery.
  • For women who did not receive screening at 35-37 weeks, an alternate strategy gives antibiotics during labor and delivery to women who:
    • Are known carriers of GBS bacteria or had GBScolonization at any time during the present pregnancy
    • Have previously had an infant with GBS disease
    • Go into labor or have rupture of the membranes before the fetus has reached an estimated gestational age of 37 weeks
    • Have rupture of membranes for 18 hours or more before delivery
    • Have a fever during labor
    • Have a urinary tract infection with GBS


Group B Strep Association

The American Congress of Obstetricians and Gynecologists


The Society of Obstetricians and Gynaecologists of Canada

Women's Health Matters


De Tejada BM, Pfister RE, Renzi G, et al. Intrapartum Group B streptococcus detection by rapid polymerase chain reaction assay for the prevention of neonatal sepsis. Clin Microbiol Infect. 2011;17(12):1786-1791.

Group B strep (GBS). Centers for Disease Control and Prevention website. Available at: Updated May 23, 2011. Accessed June 19, 2014.

Group B strep infection: GBS. American Pregnancy Association website. Available at: Updated March 2011. Accessed June 19, 2014.

Group B streptococcal infection in infants less than 3 months old. EBSCO DynaMed Plus website. Available at: Updated September 10, 2016. Accessed September 23, 2016.

Ohlsson A, Shah VS. Intrapartum antibiotics for known maternal Group B streptococcal colonization. Cochrane Database Syst Rev. 2009;(3):CD007467.

Puopolo KM, Madoff LC, Eichenwald EC. Early-onset Group B streptococcal disease in the era of maternal screening. Pediatrics. 2005;115(5):1240-1246.

Woodgate P, Flenady V, Steer P. Intramuscular penicillin for the prevention of early onset Group B streptococcal infection in newborn infants. Cochrane Database Syst Rev. 2004;(3):CD003667.

Last reviewed June 2016 by Michael Woods, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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