Group B Streptococcus and Pregnancy

Your Guide to a Healthy Pregnancy

What is Group B Streptococcus?

Group B Streptococcus (GBS) is a common bacteria (germ) that is present in up to 40 percent of pregnant women.  A women with GBS can pass the bacteria to her infant while she is pregnant, during delivery, or after the birth.  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.

What infections can Group B Streptococcus cause?

In the pregnant women, GBS can cause bladder infections, blood infections, skin or soft tissue infections, bone and joint infections, pneumonia, womb infections (amnionitis, endometritis), and can even cause stillbirth.

In newborns, GBS is the most common cause of sepsis (a blood infection) and meningitis (an infection of the fluid and lining surrounding the brain).  It is also a frequent cause of pneumonia.

How does a baby get GBS?

GBS is a common bacteria that lives in the mouth/throat, bladder, reproductive tract, and rectum of men and women.  In women, GBS is found most frequently in the vagina and rectum.  GBS can live in a pregnant woman’s body and cause symptoms and an infection.  GBS can also live in a pregnant women’s body and not cause any symptoms and not pose any danger to her health.  In this situation, the woman is called a “carrier”.  A pregnant woman can pass GBS to her baby when she has an active GBS infection and when she is simply a carrier of the bacteria.  A mother who has GBS in her rectum or vagina at the time of delivery might infect a newborn with GBS.

Some statistics:

  • Approximately one out of every 100 to 200 babies whose mothers are GBS carriers develop GBS-related infections.
  • About 10 percent to 15 percent of babies develop GBS-related meningitis.  Babies who develop meningitis might have long-term problems, such as hearing or vision loss, or learning disabilities.
  • Up to 15 percent of babies with GBS die from their infections.

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 1 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.

Can I be tested for GBS?

GBS can be detected during pregnancy by using a cotton swab to take samples of cells from the vagina, cervix and rectum.  This test is simple and will not hurt.  The sample will capture GBS bacteria if present, is placed in a special material to grow (this takes a few days).  At that point, a diagnosis can be made.  A GBS infection can also be diagnosed from samples of blood, spinal fluid or urine.

Your doctor will test you for GBS late in your pregnancy – around week 36 to 37.  Testing for GBS earlier than this will not help predict if you will have GBS at the time of delivery.  This is because GBS might be detected at one point in time and not at other times.

The ability to detect GBS can change from one test site to another at different points in time.  Delivery is a time of increased exposure to GBS bacteria for newborns if it is present in the vagina or rectum of the mother.  Therefore, the closer to delivery your doctor tests you, the more confident he or she will be in determining if you have a GBS and in deciding upon a course of action.  A positive culture result means you are a GBS carrier, but it does not mean that you or your baby will definitely become ill.

How will my doctor decide what to do?  Are some women (and their babies) at higher risk for developing GBS infections?

Since not all GBS carriers definitely pass GBS to their newborns and not all babies get GBS and become ill, your doctor will need to decide if treating you makes sense.  GBS carriers at greater risk of passing GBS to their newborns – and for whom treatment is most beneficial – are women with any of the following conditions:

  • Women who undergo pre-term labor or have their membranes rupture (the breaking of the fluid-filled amniotic sac in the mother’s uterus in which the fetus develops – the so-called “water-breaking” event) before week 37 of pregnancy.
  • Women who experience prolonged labor – more than 18 hours since their “water” broke.
  • Women who experience fever (>100.4 F) during their labor (a sign of infection)

How is 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.  Since the ability to detect GBS changes from time to time and because being a GBS carrier is a temporary situation (people who carry GBS are typically not life-long carriers of the bacteria), treating you earlier in your pregnancy would not guarantee that you would be free of GBS at the time of delivery.

    If your doctor chooses to treat you, he or she will give you an antibiotic – for example, penicillin or ampicillin – 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. 

  • 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.  Your doctor might take a sample of the baby’s blood or spinal fluid if he or she suspects that your baby has a GBS infection.  Antibiotics will be given if treatment is determined to be necessary.