Health Library

Group B streptococcal (GBS) disease is a bacterial infection. These bacteria live in the gastrointestinal and genitourinary tracts. They 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 . 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 three ways:

• Before birth, bacteria in the vagina 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 with the mother

Vaginal Bacteria Spreading to Fetus

Copyright © Nucleus Medical Media, Inc.

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

• Mother currently has GBS in her vaginal or rectal area—This is confirmed by a lab test between weeks 35-37 of pregnancy.
• 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 gestation
• Rupture of the membranes for 18 hours or more before delivery
• Mother has a fever during labor

In pregnant women, GBS infections can sometimes cause inflammation or irritation of the lining of the uterus (endometritis), infection of the uterus and amniotic sac (amnionitis), and septic abortion (loss of pregnancy due to infection). 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 both kinds 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 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.

Methods to prevent GBS 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 carriers of GBS bacteria
  • Have previously had an infant with 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.