Group B streptococcus (also called Group B strep or GBS) is a common type of bacteria (tiny organisms that live in and around your body) that can cause infection. Usually GBS is not serious for adults, but it can hurt newborns.

Many people carry Group B strep bacteria and don’t know it. It may never make you sick. GBS in adults usually doesn’t have any symptoms, but it can cause some minor infections, like a bladder or urinary tract infection (UTI).

While GBS may not be harmful to you, it can be very harmful to your baby. If you’re pregnant, you can pass it to your baby during labor and childbirth.

About 1 out of 4 pregnant women (25 percent) carry GBS bacteria. The best way to know if you have GBS is to get tested. If you do have GBS, though, there’s good news: your health care provider can give you treatment during labor and birth that protects your baby from GBS.

How do you get GBS?

GBS bacteria live in the intestines and the urinary and genital tracts. It lives in the body naturally. As an adult, you can’t get it from food, water or things you touch. You can’t catch it from another person, and you can’t get it from having sex.

How do you know if you have GBS?

Your provider tests you for GBS at 35 to 37 weeks of pregnancy. Testing for GBS is simple and painless. Your provider takes a swab of your vagina and rectum and sends the sample to a laboratory. Your test results are usually available in 1 to 2 days.

Your provider also can use some quick screening tests during labor to test you for GBS. But these should not replace the regular GBS test that you get at 35 to 37 weeks of pregnancy.

How can you protect your baby from GBS?

If your GBS test at 35 to 37 weeks shows you have the infection, your provider gives you medicine called an antibiotic during labor and birth through an IV (through a needle into a vein). You also may be treated if you have any risk factors for GBS and you don’t know your GBS test results or you haven’t been tested yet. Treatment with antibiotics helps prevent your baby from getting the infection.

Penicillin is the best antibiotic for most women. Another antibiotic called ampicillin also can be used. These medicines usually are safe for you and your baby. But some women (up to 1 in 25 women, or 4 percent) treated with penicillin have a mild allergic reaction, like a rash. About 1 in 10,000 women have a serious allergic reaction that needs to be treated right away. If you’re allergic to penicillin, your provider can treat you with a different medicine.

If your test shows you have GBS, remind your health care providers at the hospital when you go to have your baby. This way, you can be treated quickly. Treatment works best when it begins at least 4 hours before childbirth.

If you have GBS and you’re having a scheduled cesarean birth (c-section) before labor starts and before your water breaks, you probably don’t need antibiotics.

It’s not helpful to take oral antibiotics before labor to treat GBS. The bacteria can return quickly, so you could have it again by the time you have your baby.

If you have GBS, what are the chances that you can pass it to your baby?

If you have GBS during childbirth and it’s not treated, there is a 1 to 2 in 100 chance (1 to 2 percent) that your baby will get the infection. The chances are higher if you have any of these risk factors:

  • Your baby is premature. This means your baby is born before 37 weeks of pregnancy.
  • Your water breaks (also called ruptured membranes) 18 hours or more before you have your baby.
  • You have a fever (100.4 F or higher) during labor.
  • You’ve already had a baby with a GBS infection.
  • You had a UTI during your pregnancy that was caused by GBS.

If you have GBS and you’re treated during labor and birth, your treatment helps protect your baby from the infection.

If your baby gets GBS, do signs of infection or other problems show up right after birth?

Not always. It depends on the kind of GBS infection your baby has. There are two kinds of GBS infections:

  1. Early-onset GBS: Signs like fever, trouble breathing and drowsiness start during the first 7 days of life, usually on the first day. Early-onset GBS can cause pneumonia, sepsis or meningitis. If you have GBS, you can pass this kind of infection to your baby. But treatment with antibiotics during labor and birth can help prevent your baby from getting it. About half of all GBS infections in newborns are early-onset.
  2. Late-onset GBS: Signs like coughing or congestion, trouble eating, fever, drowsiness or seizures usually start when your baby is between 7 days and 3 months old. Late-onset GBS can cause sepsis or meningitis. If you have GBS, you can pass this kind of infection to your baby during or after birth. Treatment with antibiotics during labor and birth does not prevent late-onset GBS. After birth, your baby also can get GBS from other people who have the infection.

What problems can GBS cause in newborns?

Babies with a GBS infection can have one or more of these illnesses:

  • Meningitis, an infection of the fluid and lining around the brain
  • Pneumonia, a lung infection
  • Sepsis, a blood infection

Pneumonia and sepsis in newborns can be life-threatening.

Most babies who are treated for GBS do fine. But even with treatment, about 1 in 20 babies (5 percent) who have GBS die. Premature babies are more likely to die from GBS than full-term babies (born at 39 to 41 weeks of pregnancy).

GBS infection may lead to health problems later in life. For example, about 1 in 4 babies (25 percent) who have meningitis caused by GBS develop:

  • Cerebral palsy (A group of disorders that can cause problems with brain development. These problems affect a person's ability to move and keep their balance and posture.)
  • Hearing problems
  • Learning problems
  • Seizures

If your baby has a GBS infection, how is he treated?

It’s important to try and prevent a newborn from getting GBS. But if a baby does get infected with early-onset GBS or late-onset GBS, he is treated with antibiotics through an IV.

If you're treated for GBS during labor, does your baby need special treatment?

Probably not. But if you have a uterine infection (an infection in your uterus) during labor and birth, your baby should be tested for GBS. Your baby’s provider can treat your baby with antibiotics while you wait for the test results.

Can GBS cause problems for mom during and after pregnancy?

GBS can cause a uterine infection during and after pregnancy. Symptoms of a uterine infection include:

  • Fever
  • Pain in your belly
  • Increased heart rate (During pregnancy, it also can cause your baby’s heart rate to increase.)

If you have a uterine infection, your provider can give you antibiotics, and the infection usually goes away in a few days. Some women have no symptoms, so they don’t get treatment. Without treatment, infection during pregnancy may increase your chances of:

  • Premature rupture of the members – When the amniotic sac breaks after 37 weeks of pregnancy but before labor starts
  • Preterm labor – Labor that happens too early, before 37 weeks of pregnancy
  • Stillbirth – When a baby dies in the womb after 20 weeks of pregnancy

If you’re treated for GBS during labor and birth, you probably won’t get a uterine infection after your baby is born.

GBS also can cause a UTI during pregnancy. A UTI can cause fever or pain and burning when you urinate. Sometimes a UTI doesn’t have any symptoms. If you have a UTI, you may find out about it from a urine test during one of your prenatal visits.

If you have a UTI caused by GBS, your provider gives you antibiotics to take by mouth during pregnancy. You also get antibiotics through an IV during labor and birth, because you may have high levels of GBS in your body.

Is there a vaccine for GBS?

No. But researchers are making and testing vaccines to prevent GBS infection in mothers and their babies.

More information

Centers for Disease Control and Prevention (CDC)

Last reviewed: November, 2013