Official reprint from UpToDate®
www.uptodate.com ©2015 UpToDate®

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
0 Find synonyms

Find synonyms Find exact match



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 digestive system and the vagina. In healthy adults, GBS is not harmful and does not cause 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 gastrointestinal system 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, infection of the amniotic fluid (bag of water), and infection of the uterus after delivery. GBS infections during pregnancy may lead to preterm labor.
  • 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), 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 culture during your current pregnancy showing GBS
  • You had an infant infected with GBS in the past


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 you urine culture shows GBS or other bacteria, you may be treated with an antibiotic. If you have symptoms of urinary infection, such as pain with urination, any time during your pregnancy, a urine culture is done. If GBS grows from the urine culture, it should be treated with an antibiotic, and you should also receive intravenous antibiotics during labor.

Expert groups recommend that all pregnant women have a GBS culture at 35 to 37 weeks of pregnancy. The culture is done by swabbing the vagina and rectum. If your GBS culture is positive, 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 and tell them 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 the penicillin. If you had a serious allergy (for example, trouble breathing, swelling of your face) you may need an additional test 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 infections 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. 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: Mar 2015. | This topic last updated: Jul 1, 2013.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2015 UpToDate, Inc.

All topics are updated as new information becomes available. Our peer review process typically takes one to six weeks depending on the issue.