Northside Health Library

Group B streptococcus - pregnancy

Alternate Names

GBS - pregnancy

What Is Group B streptococcus (GBS)?

Group B streptococcus (GBS) is a type of bacteria that some women carry in their intestines and vagina. It is not passed through sexual contact.

Most of the time, GBS is harmless. However, GBS can be passed to a newborn during birth:

Most babies who come in contact with GBS during birth will not become sick. But the few babies who do become ill can have severe problems.

GBS Infection in Newborn Babies

After your baby is born, GBS can lead to infections in:

  • The blood (sepsis)
  • The lungs (pneumonia)
  • The brain (meningitis)

Most babies who get GBS will start having problems during their first week of life. Some babies will not get sick until later. Symptoms can take as long as 3 months to appear.

The infections caused by GBS are serious and can be fatal. Yet prompt treatment can lead to complete recovery.

Preventing GBS Infections in Babies

Women who carry GBS often don’t know it. You are more likely to pass the GBS bacteria to your baby if:

  • You go into labor before week 37.
  • Your water breaks before week 37.
  • It has been 18 or more hours since your water broke, but you haven’t had your baby yet.
  • You have a fever of 100.4°F or more during labor.
  • You have had a baby with GBS during another pregnancy.
  • You have had urinary tract infections that were caused by GBS.

When you are 35 - 37 weeks pregnant, your doctor may do a test for GBS. The doctor will take a culture by swabbing the outer part of your vagina and rectum. The swab will be tested for GBS. Results are often ready in a few days.

Some doctors do not test for GBS. Instead they will treat any woman who is at risk for having their baby be affected by GBS.

Treating and Preventing GBS Infections in Pregnant Women

There is no vaccine to protect women and babies from GBS.

If a test shows that you carry GBS, your doctor will give you antibiotics through an IV during your labor. Even if you are not tested for GBS but have risk factors, your doctor will give you the same treatment.

There is no way to avoid getting GBS.

  • The bacteria are widespread. People who carry GBS often have no symptoms. GBS can come and go.
  • Testing positive for GBS does not mean you will have it forever. But you will still be considered a carrier for the rest of your life.

Note: Strep throat is caused by a different bacterium. If you have had strep throat, or got it while you were pregnant, it does not mean that you have GBS.

Review Date: 5/31/2012
Reviewed By: Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Bellevue, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.
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