All About the Group B Streptococcus Test

Group B Streptococcus (GBS) is a Streptococcus Bacteria are usually found in the digestive or urinary tract. It’s usually harmless to adults, but can be a dangerous, even fatal infection in newborns.

If you are pregnant, your healthcare provider may recommend a group B strep test at 36 or 37 weeks. A simple test to determine if you have group B strep bacteria can be treated shortly before delivery to help prevent infection in your baby.

This article explains the purpose and possible outcomes of the group B strep test.

Purpose of the Group B Streptococcus Test

GBS is usually present in the vagina or rectum and can be transmitted to the baby during vaginal delivery.

GBS is the most common cause meningitis in newborns. It can also cause pneumonia or sepsis (blood infection).

This test determines whether pregnant women have GBS so that they can be treated with antibiotics before giving birth.

Pregnant women treated with GBS bacteria have a 1 in 4,000 chance of having a baby with GBS, or developing GBS shortly after birth. Untreated pregnant women have a 1 in 200 chance of having a baby with GBS.

How Common is Group B Streptococcus?

About 25% of pregnant women have group B strep bacteria in their bodies. Because of testing, only about 2,000 babies are born or develop GBS each year in the United States.

what to expect

You don’t need to prepare for this test. They are simple tests used to obtain samples that are sent to a laboratory for analysis. The results will be sent back to your provider’s office and they will communicate with you.

Pregnant women and babies have different types of group B strep tests.

Adult Group B Test

  • Swab test: You’ll lie on an exam table and your healthcare provider will use a cotton swab to take a sample of cells from your vagina and rectum.
  • Urine test: You will be asked to pee in a cup. Before filling the cup, urinate a little in the toilet to help keep the sample sterile.

Infant Group B Test

  • Blood test: The healthcare provider will use a small needle to take a blood sample from your baby’s heel. It might sting a little.
  • Spinal tap: The medical team will insert a needle into the baby’s back to get a sample of spinal fluid. The area will be numb so that the baby does not feel pain. It takes about five minutes.


Positive Outcomes for Pregnant Women

If the test is positive, your healthcare provider will give you antibiotics during labor by IV (intravenous), which is more effective than taking antibiotic pills.

Once you are in active labor, you may receive treatment right away. Ideally, antibiotics should be started at least four hours before delivery to give them the best chance of preventing infection in your baby.

Newborn positive result

If the baby tests positive for GBS, they will be given antibiotics by IV right away. If the baby is symptomatic, a healthcare provider may start testing before the results are available, as GBS can cause serious illness and, in rare cases, can be fatal if an infection such as sepsis, pneumonia or meningitis develops.

Antibiotics are required for up to 14 days, usually in the neonatal intensive care unit (NICU).


Pregnant women are recommended to be tested for group B streptococcus to help prevent serious infections in their newborns. This is a quick and easy test. If you test positive, you will be given antibiotics right after delivery. They will be given repeatedly every few hours until delivery, which will kill the bacteria, making it less likely to infect your baby. GBS infection is not usually dangerous in adults, but can be serious or life-threatening in infants.

VigorTip words

Group B strep is rare in the United States because most pregnant women are tested to identify the bacteria and receive treatment to protect their babies. The test is a simple procedure that can prevent serious illness in newborns. If you have any concerns about the test, please discuss it with your healthcare provider.

Frequently Asked Questions

  • What happens if I test positive for Group B Streptococcus?

    If you test positive, your healthcare provider will arrange for you to have intravenous antibiotics during labor. This will greatly reduce the risk to the baby.

  • Is Neonatal Streptococcus B Curable?

    Strep B can be cured with antibiotics in newborns, but must be given rapidly by intravenous injection for up to 14 days. If babies develop symptoms of meningitis or other serious infections, they will be treated. Most babies recover, but 1 in 16 babies can be fatal if GBS develops.

  • What are the symptoms of group B strep?

    Adults are usually asymptomatic, but infants may be irritable, sleepy, grunt, or have trouble breathing. If you notice symptoms in your baby, seek medical attention right away.