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Group B Strep and Pregnancy

Unless you have been pregnant before, you’ve probably never heard of group B streptococcus (GBS), also called “group B strep” or “baby strep.” That’s because most people who have GBS don’t know that they have it and experience no problems.

But when you’re pregnant, having this infection can be harmful to your baby, so it’s important to know what it is and what to do about it.

About Group B Strep

Many different types of bacteria live in the human body. Some are good for the body and help it to work correctly, and others cause illness. GBS is one of the many bacteria that can live in the body and usually don’t cause any problems. It is typically found in the urinary, digestive, and reproductive tracts.

Because GBS can naturally come and go from the body without producing any health effects, most people do not know if and when they have it. About 25% of pregnant women carry this bacterium in their bodies.

It’s important to know that having GBS does not mean a woman is “unclean” in any way or did anything to contract the bacteria. Also, although the names are similar, GBS is different from group A strep, which is the bacterium that causes strep throat.

Effects on the Body

Although GBS generally does not cause any problems, some people who have it get sick. Elderly people and those with chronic medical conditions, such as diabetes, cancer, and liver disease, are more likely to become ill if they have GBS. The most common problems of GBS in adults are infection of the blood (sepsis), lungs (pneumonia), skin, and bones.

In pregnant women, GBS also can cause infection of the urinary tract, placenta, womb, and amniotic fluid. Women also can pass the infection to their babies during labor and delivery.

Effects on Babies

Most babies who are exposed to GBS from their mothers do not have any problems. However, some become very sick and can even die from it. Premature babies are more likely to be harmed by GBS infection than full-term babies because their bodies and immune systems are less developed.

The two types of GBS disease in babies are:

  1. Early-onset infections, the most common type, occur during the first week of life. They usually cause problems right away, within 24 hours after birth.
  2. Late-onset infections develop in babies weeks to months after birth. This type of GBS disease is not well understood, as the source of the infection is commonly unknown (it may pass from the mother or from another source, for example).

Signs and symptoms of GBS disease in newborns and infants can include:

  • fever
  • feeding problems
  • breathing problems
  • irritability or fussiness
  • inactivity or limpness
  • inability to maintain an adequate body temperature

Babies with GBS disease also can develop other serious problems, such as pneumonia, sepsis, and infection of the fluid and lining around the brain (meningitis). Meningitis is more common with late-onset GBS disease and can lead to hearing and vision loss, learning disabilities, seizures, and even death.


Pregnant women are routinely tested for GBS late in the pregnancy, usually between weeks 35 and 37. The test is simple, inexpensive, and painless. Called a culture, it involves using a large cotton swab to collect samples from the vagina and rectum. These samples are analyzed in a lab to determine whether GBS is present. The results of GBS testing are usually available within 1 to 3 days.

When a test detects the presence of GBS, the woman is said to be “GBS positive.” This result means only that she has the bacteria in her body — not that she or her baby will become sick from it.

GBS infection in babies is diagnosed by analyzing a sample of blood or spinal fluid. However, not all babies born to GBS-positive mothers need to undergo this testing. Most healthy babies are simply observed to see whether they have signs of infection.

Treatment and Prevention

Although nothing can be done to stop pregnant women from getting GBS, doctors have found a safe and simple way to help prevent early-onset GBS disease in newborn babies.

The first step is to test the mother and find out whether she has GBS. If she does, she is given intravenous (IV) antibiotics during labor to kill the bacteria. Penicillin is the antibiotic that is most commonly given; however, other medicines can be used if a woman is allergic to penicillin.

Ideally, the woman should receive them for at least 4 hours prior to delivery. This simple step greatly helps to prevent the spread of GBS to the baby. Unfortunately, antibiotics cannot be used before labor to help prevent the spread of the infection to the baby because GBS bacteria usually grow back quickly.

In addition to women who test positive for GBS, other women may be given antibiotics during labor, including those who:

  • go into labor before being tested for GBS (premature labor)
  • have not been tested for GBS and have prolonged membrane rupture (water breaks 18 or more hours before delivery)
  • have not been tested for GBS and have a fever during labor
  • experienced a GBS bladder infection during the pregnancy
  • have had a previous infant with GBS disease

Babies who get GBS disease are also treated with antibiotics. This treatment should begin as soon as possible to help prevent problems. These babies also may need other treatments, like breathing help and IV fluids.

Unfortunately, giving antibiotics during labor only helps to prevent early-onset GBS disease, not late-onset disease. Because the cause of late-onset disease is unknown, no method has yet been identified to prevent it. However, researchers are working to develop a vaccine to prevent GBS infection.


The outlook for women who test positive for GBS and receive antibiotics at the appropriate time during labor is good. Most women do not pass the infection to their babies. Women who are GBS-positive can safely breastfeed.

Since GBS comes and goes from the body, all women should receive GBS testing each time they are pregnant, regardless of their previous results. Testing and timely treatment can greatly help to reduce the occurrence of this preventable disease and its potentially devastating effects.

Reviewed by: Elana Pearl Ben-Joseph, MD
Date reviewed: April 2014