Group B Streptococcus (GBS) in Pregnant Women and Infants: Commonly Asked Questions

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What is Group B Streptococcus (GBS)?

GBS is a germ that is found normally in the intestines and genital tract of about one out of five pregnant women.

Although it usually is not harmful to the woman, it can cause serious infections in her baby, including infections of the blood, spinal fluid and lungs. It is the most common cause of these types of serious infections in newborns.

Not every woman who has GBS in the intestines and genital tract will have a baby with serious infection. Approximately 1 out of 150 babies of mothers who have the germ will develop signs of infection and most of these will occur in the first week of life.

There are some factors that increase the chance that a woman will have a baby with GBS disease (see following section).

GBS can also cause disease in pregnant women, including urinary tract infections and womb infections. Also people with other illnesses like diabetes or liver disease, or the elderly can have infections with GBS.

What can be done to help prevent GBS disease in my baby?

In August 2002, the U.S. Centers for Disease Control and Prevention (CDC) updated recommendations on the prevention of the type of GBS infection that occurs in babies shortly after birth. These guidelines advise health care providers to use a screening-based approach to decide which woman may benefit from getting an antibiotic (like penicillin) through the vein during delivery.

Providers use a screening test to see if their patients carry GBS. This test is done by swabbing the vagina and rectum between the 35th and 37th week of pregnancy. Women who have a positive screening test for GBS, can benefit from receiving antibiotics during labor.

Women who have had a previous baby that had a GBS infection or women who during the current pregnancy have a urinary tract infection with GBS, have an increased risk of having a baby with GBS infection and can benefit from receiving antibiotic during labor. These women do not need to be screened during pregnancy.

There are risks that are associated with an increased chance of a woman having a baby with GBS that occur around the time of labor and delivery. These include:

  • Fever during labor,
  • Membranes rupture (water break) for 18 or more hours prior to delivery, or
  • Preterm labor (before 37 weeks).

Women who were not screened for GBS, but have one of these factors, can benefit from receiving antibiotics during labor.

What research is being done on prevention of GBS?

Even though the prevention approaches are very effective, some babies may still get GBS infection.

Research on a GBS vaccine is ongoing. In the future this may help decrease the risk of GBS disease even more.


If you have questions about GBS, please talk with your health care provider.

Updated Monday, July 07, 2014 at 09:41AM