Group B Strep (GBS) Test
Reviewed
Also called: Group B Streptococcus, Group B Beta-Hemolytic Streptococcus, Streptococcus agalactiae, Beta-hemolytic strep culture
Strep B, also known as group B strep (GBS), is a type of bacteria commonly found in the digestive tract, urinary tract, and genital area.
Specimen: Swab from vagina and rectum, or urine (clean-catch), or blood (heel stick in newborns), or cerebrospinal fluid (lumbar puncture in newborns)
Why this test may be ordered
- Routine prenatal screening between 36 and 38 weeks of pregnancy
- If labor begins before 36 weeks
- Newborns with signs of infection such as fever, trouble feeding, trouble breathing, lack of energy, irritability, bluish skin, unstable blood pressure, or kidney problems
- Symptoms of GBS disease in non-pregnant adults: fever, chills, low alertness, cough, rapid breathing, chest pain, red/swollen/painful skin bumps with pus, bone/joint pain with swelling or stiffness
Preparation and collection
You don't any special preparations for group B strep tests.
If you are pregnant, your health care provider may order a swab test or a urine test. Your provider will use a small cotton swab to take a sample of cells and fluids from your vagina and rectum. If your baby needs testing, a provider may do a blood test or a lumbar puncture (spinal tap).
There is no risk to you from a swab or urine test. Your baby may have slight pain or bruising after a blood test, but that should go away quickly. Your baby will likely feel some pain after a spinal tap, but that shouldn't last too long. There is also a small risk of infection or bleeding after a lumbar puncture.
Understanding results
If a result or symptoms suggest an emergency, get emergency medical help right away.
Many healthy people have GBS bacteria in their bodies. Most of the time, GBS bacteria are not harmful and do not make people feel sick or have any symptoms.
- GBS found during pregnancy: If you are pregnant and results show you have GBS bacteria, you will be given antibiotics intravenously (by IV) during labor, at least four hours before delivery. This will prevent you from passing the bacteria to your baby. Limitation: Taking antibiotics earlier in your pregnancy is not effective, because the bacteria can grow back very quickly. Next step: If you have questions about your results or your baby's results, talk to your provider.
- GBS infection found in your baby: If your baby's results show a GBS infection, he or she will be treated with antibiotics. Limitation: If your provider suspects a GBS infection, he or she may treat your baby before test results are available. This is because GBS can cause serious illness or death. Next step: If you have questions about your results or your baby's results, talk to your provider.
- GBS bacteria can grow back quickly after antibiotics, so treatment earlier in pregnancy is not effective.
- In newborns, early-onset GBS disease symptoms usually appear on the day of birth; late-onset can appear between 7 and 89 days of life, and the source is unknown.
- If your provider suspects a GBS infection, treatment may begin before test results are available because GBS can cause serious illness or death.
What to do next
You may not need antibiotics if you are having a planned cesarean delivery (C-section). But you still should be tested during pregnancy because you may go into labor before your scheduled cesarean delivery. If you have questions about your results or your baby's results, talk to your provider.
- What does a positive GBS test mean for my labor and delivery?
- If my baby tests positive, what treatment will be given?
- Do I need antibiotics if I have a planned C-section?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.