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Patient information: Group B streptococcus and pregnancy (Beyond the Basics)

Karen M Puopolo, MD, PhD
Carol J Baker, MD
Section Editors
Charles J Lockwood, MD, MHCM
Daniel J Sexton, MD
Deputy Editor
Vanessa A Barss, MD, FACOG
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Group B streptococcus (GBS) is a bacterium that can cause serious infections in pregnant women and newborn babies. GBS is one of many types of streptococcal bacteria, sometimes called "strep."

This article discusses GBS, its effect on pregnant women and infants, and ways to prevent complications of GBS. More detailed information about GBS is available by subscription. (See "Group B streptococcal infection in pregnant women".)


GBS is commonly found in the lower part of the digestive system (colon) and, in women, the vagina. In healthy adults, GBS is not harmful and does not cause medical problems. But in pregnant women and newborn infants, being infected with GBS can cause serious illness.

Approximately one in three to four pregnant women in the US carries GBS in their intestinal tract and/or in their vagina. Carrying GBS is not the same as being infected. Carriers are not sick and do not need treatment during pregnancy. There is no treatment that can stop you from carrying GBS.

Pregnant women who are carriers of GBS infrequently become infected with GBS. GBS can cause urinary tract infections (typically involving only the bladder), infection of the amniotic fluid (“bag of water” surrounding the fetus), and infection of the uterus after delivery. GBS infections during pregnancy may lead to preterm labor or stillbirth.

Pregnant women who carry GBS can pass on the bacteria to their newborns, and some of those babies become infected with GBS. Newborns who are infected with GBS can develop pneumonia (lung infection), septicemia (blood infection), and/or meningitis (infection of the lining of the brain and spinal cord).

These complications can be prevented by giving intravenous antibiotics during labor to any woman who is at risk of GBS infection. You are at risk of GBS infection if:

You have a urine culture during your current pregnancy showing GBS

You have a vaginal and rectal swab culture during your current pregnancy showing GBS

You had an infant infected with GBS in the past

If you go into labor and have not had a culture for GBS in your current pregnancy or a previously affected infant, you are at risk for GBS if:

You go into labor prematurely (more than three weeks before your due date)

You have a fever ≥100.4 degrees Fahrenheit during labor

You have ruptured membranes for ≥48 hours


Most doctors and nurses recommend a urine culture early in your pregnancy to be sure that you do not have a bladder infection without symptoms. If your urine culture shows GBS or other bacteria, you may be treated with an antibiotic. If you have symptoms of urinary infection, such as burning pain with urination, any time during your pregnancy, a urine culture should be done. If GBS grows from the urine culture, this infection should be treated with an antibiotic, and you should also receive an intravenous antibiotic during labor.

Expert groups recommend that all pregnant women have a GBS swab culture at 35 to 37 weeks of pregnancy. The culture is done by swabbing the vagina and rectum. If your GBS culture is positive for GBS, you will be given an intravenous antibiotic during labor. If you have preterm labor, the culture is done then and an intravenous antibiotic is given until the baby is born or the labor is stopped by your health care provider.

If you have a positive GBS culture and you have an allergy to penicillin, be sure your doctor and nurse are aware of this allergy early in your pregnancy and tell them exactly what happened with the allergy. If you had only a rash or itching, this is not a serious allergy, and you can receive a common drug related to penicillin. If you had a serious allergy (for example, trouble breathing, swelling of your face, or hives) and you carry GBS, your GBS should be tested in the laboratory to determine which antibiotic should be used during labor.

Being treated with an antibiotic during labor greatly reduces the chance that you or your newborn will develop a serious infection related to GBS.

It is important to note that young infants up to age 3 months can also develop septicemia, meningitis and other serious infections from GBS. Being treated with an antibiotic during labor does not reduce the chance that your baby will develop this later type of infection that begins after the first week of life. There is currently no known way of preventing this later-onset GBS disease.


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient information: Avoiding infections in pregnancy (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

This topic currently has no corresponding Beyond the Basics content.

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Neonatal group B streptococcal disease: Prevention
Group B streptococcal infection in neonates and young infants
Group B streptococcal infection in pregnant women
Group B streptococcal infections in nonpregnant adults
Group B streptococcus: Virulence factors and pathogenic mechanisms
Vaccines for the prevention of group B streptococcal disease

The following organizations also provide reliable health information.

National Library of Medicine


The Center for Disease Control and Prevention (available in Spanish)



Literature review current through: Oct 2015. | This topic last updated: May 12, 2015.
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