I have heard a lot of questions about group B streptococcus (GBS) from my patients this week. So here’s some info to answer all of the questions you might have about GBS.

What is group B streptococcus (GBS)?
Group B streptococcus is one of the many types of bacteria that live in the body and usually do not cause serious illness. It is found in the digestive, urinary, and reproductive tracts of men and women. In women, it can be found in the vagina and rectum. GBS is not a sexually transmitted infection. GBS is found in about 25 percent of all healthy, adult women.

Why is GBS a concern for pregnant women?
Most pregnant women who are colonized with GBS have no symptoms or health effects. In a small number of women, GBS can cause infections of the uterus and urinary tract. A woman who is colonized with GBS late in her pregnancy can pass it to her baby. GBS affects about 1 in every 2,000 babies born in the United States.

How does GBS affect a newborn baby?
GBS infections occur during the first week of life, generally within the first 24 to 48 hours after birth. These infections can occur as the baby moves through the birth canal of a woman who is colonized with GBS. Only a few babies who are exposed to GBS develop an infection. Certain factors, such as preterm birth, may increase the risk of a baby becoming infected. The most common problems caused by early-onset GBS infections are lung infections, blood infections, and meningitis.

When are pregnant women tested for GBS?
To help prevent GBS infection in newborns, women are tested for GBS late in pregnancy, between weeks 35 and 37. The test is called a culture. In this test, a swab is used to take a sample from the woman’s vagina and rectum. This procedure is quick and not painful. The sample is sent to a lab where it is grown in a special substance.

What if the test results are positive?
If results of the culture test are positive, showing that GBS is present, you most likely will receive treatment with antibiotics during labor to help prevent GBS from being passed to your baby. Antibiotics help get rid of some of the bacteria that can harm the baby during birth. The antibiotics work only if they are given during labor. If treatment is given earlier in pregnancy, the bacteria may regrow and be present during labor. Penicillin is the antibiotic that is most often given to prevent early-onset GBS infection in newborns. (If you are allergic to penicillin, tell your healthcare provider before you are tested for GBS. Women with mild allergic reactions can take an antibiotic called cefazolin. If you have had a severe reaction to penicillin, such as hives or anaphylaxis, the bacteria in the sample need to be tested to determine the choice of antibiotic.)