Learning About Your Health

Group B Streptococcus (GBS) Screening

What is Group B Streptococcus (GBS)?

  • Group B streptococcus (GBS) is a type of bacteria that can cause illness in newborn babies.

  • Adults can carry GBS in their intestines and in the vagina, but do not become ill. These people are considered to be "carriers."

  • People who carry GBS typically do so temporarily – that is, they do not have the bacteria for their whole life.

  • 1 out of every 5 to 6 pregnant women carries GBS in the rectum or vagina.

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Why is it Important to Get a GBS Screening Test?

  • It is important to have a GBS screening during your pregnancy because GBS can cause illness in newborn babies. GBS is the most common cause of life-threatening infections in newborns.

  • Your baby may come in contact with GBS during birth if you are a carrier. A small number of babies whose mothers carry GBS develop signs and symptoms of the disease. These are the babies we are trying to protect.

  • Nearly all GBS infections in newborns can be prevented. Antibiotics work very well to prevent the spread of GBS from mother to baby.
NOTE: With screening, GBS is now a rare problem (less than 1 per 1000 births).*


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How is GBS Screening Done?

The doctor takes a swab from the vagina and rectum in late pregnancy (35-37 weeks) to test for GBS bacteria. This test is like a pap smear. A "positive" result means that the mother carries GBS – not that she or her baby will get sick.

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What if my GBS Test is Positive?

Women who test "positive" for GBS receive antibiotics intravenously (IV) when labor begins or when the bag-of-water breaks (rupture of membranes). For women who go into preterm labor before a GBS screen has been done, a culture is taken in the hospital and antibiotics may be given, if needed. Also, any pregnant woman who has had a baby with GBS disease in the past or a urinary tract infection during this pregnancy caused by GBS should receive antibiotics during labor.

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When are Antibiotics for GBS Given?

Antibiotics are given at least four (4) hours before the baby is born. If you are allergic to penicillin, please remind your doctor.

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The Results of Your Screening

The results of your screening will be ready in 2-3 days.

Please bring the results of your GBS screening test with you when you come to the hospital for any reason.

Your GBS screen was:
__ Positive
__ Negative
Date _________________


*Schrag, S., Gorwitz, R., Futlz-Butts, K., et. al. Prevention of Perinatal Group B Streptococcal Disease. Revised Guidelines from CDC. Morbidity and Mortality Weekly (MMWR). 2002 Aug 16;51 (RR-11):1-22.

Produced by the Center for Patient and Community Education in association with the Women and Children's Center at California Pacific Medical Center. Date: 3/06

© 2006-2008 California Pacific Medical Center

Funded by: A generous donation from the Mr. and Mrs. Arthur A. Ciocca Foundation.

Note: This information is not meant to replace any information or personal medical advice which you get directly from your doctor(s). If you have any questions about this information, such as the risks or benefits of the treatment listed, please ask your doctor(s).

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