Group B Streptococcus & Pregnancy


What is Group B Streptococcus (GBS)?

Group B Streptococcus (GBS) is a normal bacteria (germ) that is present in up to 10 to 30 percent of pregnant women. A woman with GBS can pass the bacteria to her infant during delivery. Most newborns who get GBS do not become ill. However, the bacteria can cause serious and even life-threatening infections in a small percentage of newborns.

How does a baby get GBS?

In pregnant women, GBS is found most frequently in the vagina and rectum. GBS is different than strep throat, which is Group A Streptococcus. GBS can live in a pregnant woman's body and cause symptoms and an infection. GBS can also live in a pregnant woman's body and not cause any symptoms and not pose any danger to her health. In this situation, the woman is called a "carrier."

Early infection: Of the babies who become infected, most of the infections (75 percent) occur in the first week of life. In fact, most infection is apparent within a few hours after birth. Sepsis, pneumonia, and meningitis are the most common problems. Premature babies face greater risk if they become infected, but most babies (75 percent) who get GBS are full-term.

Late infection: GBS infection might also occur in infants one week to several months after birth. Meningitis is more common with late-onset GBS-related infection than with early-onset infection. About half the babies who develop late-onset GBS got the infection passed to them from their mothers during birth. The source of the infection for others with late disease is thought to be contact with other people who are GBS carriers, or the GBS "carrier" mother after birth, or perhaps still other unknown sources. Late-onset infection is less common and is less likely to result in a baby's death than early-onset infection.

Diagnosis and Tests

Will I be tested for Group B Streptococcus (GBS)?

Your doctor will test you for GBS late in your pregnancy, around week 35 to 37, by using a cotton swab to take samples of cells from the vagina, cervix, and rectum. Testing for GBS earlier than this will not help predict if you will have GBS at the time of delivery.

Delivery is a time of increased exposure to GBS bacteria for newborns if it is present in the vagina or rectum of the mother. A positive culture result means you are a GBS carrier, but it does not mean that you or our baby will definitely become ill.

Management and Treatment

How is Group B Streptococcus (GBS) treated?

In the pregnant mother: The most effective way to prevent GBS infection in your baby is to treat you with antibiotics during labor if you test positive as a carrier of GBS. Being a carrier of GBS is a temporary situation it is important to treat at the time of labor as it is not effective to treat at an earlier time.

If you test positive your provider will treat you with an antibiotic administered through a vein during your labor and delivery. Giving you an antibiotic at this time helps prevent the spread of GBS from you to your newborn; 90 percent of infections are prevented by this protocol.

One exception to the timing of treatment is when GBS is detected in urine. When this is the case, oral antibiotic treatment should begin at the time GBS is identified regardless of stage of pregnancy and be given again intravenously during labor.

Any pregnant woman who has previously given birth to a baby who developed a GBS infection, who has had a urinary tract infection in this pregnancy caused by GBS, will also be treated during labor.

In the newborn: Despite testing and antibiotic treatment during a pregnant woman's labor, some babies still get GBS infections. Common symptoms of GBS infection in newborns are fever, difficulty feeding, irritability, or lethargy (limpness or difficulty in waking up the baby). Your doctor might take a sample of the baby's blood or spinal fluid to see if the baby has GBS infection. Antibiotics will be given if treatment is determined to be necessary.

Last reviewed by a Cleveland Clinic medical professional on 01/01/2018.


  • American Pregnancy Association. ( Accessed 1/1/2018.
  • The National Women's Health Information Center. Healthy Pregnancy. ( Accessed 1/1/2018.

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