Group B Streptococcus (GBS) is a bacterium commonly found in the gastrointestinal and genital tracts of many healthy adults. For most individuals, including pregnant people, colonization with GBS is harmless and does not cause symptoms or illness. Because this colonization can be temporary, a routine screening test is offered to all pregnant women in the third trimester to determine their status near the time of delivery. This testing is typically performed between the 35th and 37th week of pregnancy.
What the Group B Strep Screening Involves
The screening is designed to be quick and non-invasive. The GBS test is performed using a sterile cotton-tipped swab to collect a sample from two specific locations.
The healthcare provider will gently swab the lower third of the vagina and then the rectum to gather a specimen for laboratory culture. Unlike other gynecological procedures, the swab does not need to reach the cervix, which helps minimize any potential for discomfort.
The entire collection process is fast, often taking only a few seconds to complete. Most people describe the sensation as a mild pressure, a quick tickle, or less intense than a routine Pap smear. The procedure is generally painless, though some individuals may experience brief discomfort due to the swabbing of sensitive areas.
The patient may be offered the option to collect the swab samples themselves in the privacy of a restroom. Once collected, the sample is sent to a lab to be cultured. This process determines if the GBS bacteria is present in the genitourinary tract.
Why GBS Screening is Important for Pregnancy
Screening for GBS is a standard part of prenatal care because a positive result identifies a risk factor that can be mitigated with simple intervention. While GBS colonization is typically asymptomatic for the mother, the primary concern lies in the possibility of vertical transmission to the newborn during labor and delivery. The bacterium can be passed to the baby as they move through the birth canal, which can lead to serious health issues for the infant.
The developing newborn does not have the immune system necessary to fight off the bacteria, making them susceptible to infection. The consequences of a GBS infection in a baby can be severe. These infections are collectively known as early-onset GBS disease, and they typically occur within the first week of life.
Potential severe outcomes include sepsis, which is a blood infection, as well as meningitis, which is the inflammation of the membranes surrounding the brain and spinal cord, and pneumonia. Performing the screening identifies the mother as a carrier, allowing clinicians to take preventative action during the birth process. This targeted approach has substantially reduced the incidence of early-onset GBS disease in newborns.
Treatment Protocols Following a Positive Result
If the GBS screening test is positive, the standard medical response is to administer intravenous (IV) antibiotics during labor. This is the most effective strategy because giving antibiotics prior to labor does not clear the bacteria permanently, and GBS can quickly recolonize the area before delivery. The timing is important; the antibiotics must be present in the mother’s bloodstream and surrounding tissues during the actual birth.
The typical medication used is Penicillin, which is effective against GBS. It is administered via an IV line every four hours until the baby is delivered. The goal is to provide at least four hours of antibiotic coverage before the baby passes through the birth canal, reducing the bacterial load.
For patients who have an allergy to Penicillin, alternative antibiotics are available to ensure the same level of protection. Clindamycin or Vancomycin are common alternatives. Receiving this treatment during labor does not mean the mother is currently ill, but rather that a preventative measure is being taken to protect the infant.