Overview

A group B streptococcus test — also known as a group B strep test — checks to see if you are infected with the group B streptococcus bacteria. It's a common bacterium in the gastrointestinal tract, but can cause serious infections in newborns. If you're pregnant, your health care provider will likely recommend a group B strep test during the third trimester.

During a group B strep test, your health care provider will swab your vagina and rectum and send the samples to a lab for testing. In some cases, you might be given instructions on how to collect the samples yourself. You'll need to repeat the group B strep test each time you're pregnant.

If the group B strep test is negative, no action is needed. If the group B strep test is positive, you'll be given antibiotics during labor to prevent group B strep disease in your baby.