Group B streptococcal (GBS) disease is a bacterial infection. These bacteria live in the gastrointestinal and genitourinary tracts and are found in the vaginal or rectal areas of 10% to 35% of all healthy adult women.

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 ]]>sepsis]]> (blood infection) and ]]>meningitis]]> (infection of the fluid and lining surrounding the brain).

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



GBS is caused by the bacteria Streptococcus agalactiae . Not all babies who are exposed to the bacteria will become infected. Newborn babies can become infected with GBS in three ways:

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

Vaginal Bacteria Spreading to Fetus

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Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. Factors that increase the risk of a baby contracting GBS include the following:

  • Mother had a previous baby with GBS disease
  • GBS bacteria present during the current pregnancy
  • Mother has a urinary tract infection]]> due to GBS
  • Labor or rupture of the membranes before 37 weeks gestation
  • Rupture of the membranes for 18 hours or more before delivery
  • Mother has a fever during labor


In pregnant women, GBS infections can cause endometritis, amnionitis, and septic abortion. Two forms of infection occur in newborns: early-onset and late-onset.

Early-onset GBS disease usually causes illness within the first 24 hours of life. However, illness can occur up to 6 days after birth. Late-onset disease usually occurs at 3 to 4 weeks of age; it can occur any time from 7 days to 3 months of age.

Symptoms of both kinds of GBS include:

  • Breathing problems
  • Not eating well
  • Irritability
  • Extreme drowsiness
  • Unstable temperature (low or high)
  • Weakness or listlessness (in late-onset disease)


GBS can be diagnosed in a pregnant woman at an Ob/Gyn 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.

Blood tests may also be done.


For Mom

If you test positive for GBS or are at high risk, your doctor may recommend giving you antibiotics through an IV during labor and delivery. Penicillin or ampicillin is usually used. If you have an allergy to those drugs, clindamycin or erythromycin may be used.

It is generally not recommended that women take antibiotics before labor to prevent GBS (unless GBS is identified in the urine). Studies have shown that it is not effective at earlier stages.

For Baby

If the doctor suspects strep B infection, a newborn might be kept in the hospital a couple of extra days for close watching (observation). If the baby is diagnosed with GBS, he or she will be treated with intravenous antibiotics for 10 days. Even with screening and antibiotic treatment, some babies can still get GBS disease.


Methods to prevent GBS include:

  • Screening pregnant women at 35-37 weeks
  • Giving antibiotics during labor and delivery to women who:
    • Are carriers of GBS bacteria
    • Have previously had an infant with invasive GBS disease
    • Have GBS bacterium in the present pregnancy
    • 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
  • Giving antibiotics (usually penicillin) to newborns who were exposed to the bacteria

A vaccine is being developed, but is not currently available.