Trusted medical advice from the
American Academy of Family Physicians.

Group B Strep Infection

What is group B strep?

Group B streptococcus, or group B strep for short, is a common kind of bacteria (germ). It can live in the intestine, the rectum, or a woman’s vagina. Group B strep doesn’t usually cause problems in healthy adults. Most of the people who get sick from group B strep are newborns who are exposed to the bacteria during birth.

About 25% of healthy pregnant women have group B strep in their bodies. A woman who has group B strep is said to be “colonized” with this germ. If you are colonized with group B strep, your baby can become infected with these germs while being born and can get sick. There is less than a 1% chance that this will happen. But because group B strep infection is so dangerous for babies, it’s important to find out if you’re colonized while you’re pregnant.

Symptoms of group B strep

Group B strep doesn’t usually cause symptoms in healthy adults.

Babies who have group B strep may develop symptoms during their first week of life. This is called early-onset disease. Or they may develop symptoms from 1 week to 3 months of life. This is called late-onset disease.

The symptoms of group B strep infection in newborns may include:

  • Fever
  • Difficulty feeding
  • Lethargy (the baby is tired, hard to wake up, limp, or inactive)
  • Difficulty breathing (with severe breathing problems, the baby’s skin, lips, or nails may turn blue)

If you notice these symptoms in your newborn, call your doctor right away.

What causes group B strep?

The group B strep bacteria come and go naturally in people’s bodies. If a pregnant woman has the bacteria in her body, she can pass it to her baby during labor and delivery. A group B strep infection happens when a baby is exposed to the bacteria while it’s being born. The bacteria can cause the baby to get sick. The most common illnesses caused by the bacteria in newborns are:

  • Pneumonia (infection in the lungs)
  • Meningitis (infection of the tissue covering the brain and spinal cord)
  • Bacteremia or sepsis (infection in the blood)

There are some factors that increase a pregnant woman’s risk of having a baby who develops group B strep disease. These include:

  • Testing positive for the bacteria late in pregnancy (35-37 weeks)
  • Having the bacteria found in your urine anytime during your pregnancy
  • Having the baby early (before 37 weeks)
  • Developing a fever during labor
  • Going a long time between when your water breaks and when you deliver (18 hours or more)
  • Having had a baby before who developed group B strep disease

How is group B strep diagnosed?

If you’re pregnant, your doctor can do a test to see if you are “group B strep positive.” This test usually is done when you are 35 to 37 weeks pregnant. To perform the test, your doctor will swab your vagina and your rectum and will send the swabs to a lab to see if the strep bacteria grow.

If you have group B strep, it’s important to understand that you aren’t sick. Also, you probably will not make your baby sick. Knowing that you carry the bacteria just helps you and your doctor make decisions that can protect your baby from infection.

Can group B strep be prevented or avoided?

Pregnant women can’t avoid having group B strep in their bodies. But passing it along to their babies is preventable. The two ways to prevent your baby from getting an early-onset group B strep infection is to:

  • Get tested for the bacteria late in pregnancy (35-37 weeks).
  • Get antibiotics during labor and delivery if you are at increased risk. This includes women who tested positive for the bacteria.

Currently there is not a way to prevent your baby from getting late-onset group B strep disease.

Group B strep treatment

If you test positive for group B strep or are at increased risk of having it, your doctor will give you antibiotics during labor. These will be given intravenously (through an IV) to kill the germs. Because the bacteria grow quickly, the antibiotics are only effective if they are given during labor. Penicillin is the most common antibiotic that doctors prescribe to treat group B strep.

If you get antibiotics while you’re in labor, the chances are very good that your baby won’t get an early-onset group B strep infection.

What if my baby has group B strep?

If your baby gets group B strep, he or she will be treated with IV antibiotics to kill the bacteria. Your baby will stay in the hospital until your doctor is sure your baby is better.

Living with group B strep

In healthy adults, group B strep doesn’t usually cause any problems. Certain groups are more likely to have complications from group B strep:

  • Infants who have group B strep can develop serious or life-threatening infections, such as meningitis, pneumonia, or sepsis.
  • Some pregnant women who have group B strep may develop an infection of the urinary tract (also called a UTI), placenta, amniotic fluid, or bloodstream.
  • Older adults and people who have a chronic illness or a weak immune system are more likely to develop problems due to group B strep infection. These problems may include infections of the skin, bloodstream, urinary tract, lungs, bones and joints, heart valve (called endocarditis), or the fluid around the brain and spinal cord.

Questions to ask your doctor

  • Is testing for group B strep infection a standard part of my prenatal care?
  • When should I schedule the test?
  • What do my test results mean?
  • If I have group B strep, how do we keep my baby from getting it too?
  • Will I need antibiotics? Are they safe for the baby?
  • Will I need a C-section, or can I still deliver my baby vaginally?
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