Group B Streptococcus (GBS) is a common bacterium found in the gastrointestinal and genital tracts of many healthy individuals. Between 10% and 30% of pregnant individuals carry the bacteria. While GBS often causes no symptoms in adults, screening during pregnancy is important for safeguarding newborn health.
Understanding Group B Strep Screening
Group B Strep (Streptococcus agalactiae) is a bacterium commonly found in the vagina and rectum. It is not a sexually transmitted infection and typically causes no illness in adults. Many carry GBS without symptoms.
The primary concern in pregnancy is potential transmission to a newborn during vaginal delivery. If passed to the baby, GBS can cause serious infections, including sepsis, meningitis, or pneumonia, which can be life-threatening for infants. These early-onset infections typically manifest within the first week of life, often within 24 hours of birth.
Screening for GBS is routinely performed during pregnancy, specifically between 36 and 37 weeks of gestation. This timing is important because an individual’s GBS status can change. Testing close to delivery provides the most accurate status for birth, with results considered valid for approximately five weeks. The standard clinical procedure involves a healthcare provider collecting a swab from both the lower vagina and the rectum. These samples are then sent to a specialized laboratory for analysis.
At-Home GBS Testing: What’s Possible?
At-home GBS testing refers to the collection of a sample by the pregnant individual using a specialized kit. A complete diagnostic test cannot be performed independently at home. These kits are provided by healthcare providers or certified laboratories, not for self-diagnosis.
The collected sample is mailed or transported to a professional laboratory for analysis. Detection and diagnosis of Group B Strep are exclusively carried out by trained laboratory personnel, ensuring accurate and reliable results crucial for guiding medical decisions.
Various at-home sample collection kits are available, including mail-in options. Some kits utilize an enriched culture medium (ECM) method, considered reliable for detecting GBS carriage. When instructions are followed precisely and the sample is analyzed by a reputable laboratory, at-home sample collection can yield dependable results.
A negative result from such a test, if taken within five weeks of delivery, is approximately 96% predictive of GBS absence at birth. However, GBS status can fluctuate, and false negative results may occur due to factors such as improper sample collection or recent antibiotic use. Given these considerations, it is important to consult with a healthcare provider before relying solely on at-home collection kits for GBS screening.
Steps for At-Home Sample Collection
Collecting a GBS sample at home requires adherence to the kit’s instructions. Before beginning, wash hands thoroughly with soap and water. Most kits include one or two sterile swabs.
The collection involves swabbing two specific areas: the lower vagina and the rectum. For the vaginal sample, insert the swab approximately 2 to 4 centimeters deep into the vagina. For the rectal sample, the same or a different swab is inserted about 1 to 2.5 centimeters beyond the anal sphincter. Avoid touching the cotton tip of the swab with anything other than the collection areas.
After collection, immediately place the swab(s) into the transport medium or tube provided in the kit. Securely close the container to maintain sample integrity. Following collection, package the sample according to the kit’s instructions and return it to the laboratory promptly. Many samples remain stable for several days if refrigerated or kept at room temperature in the transport media, but timely submission is recommended.
Understanding Your GBS Test Results
A positive GBS test result indicates Group B Strep bacteria were detected in the sample, meaning the individual is colonized. This finding does not imply the pregnant person is ill or that the baby will certainly become sick, but signifies a possibility of GBS transmission to the newborn during birth. Conversely, a negative GBS test result means the bacteria were not detected at the time the sample was collected.
For individuals with a positive result, healthcare providers typically recommend receiving intravenous (IV) antibiotics during labor. This preventative measure, often involving penicillin or ampicillin, significantly reduces the risk of GBS transmission to the baby, decreasing the chance from approximately 1 in 200 to about 1 in 4000. Antibiotics are most effective when administered at least four hours before delivery.
If the test result is negative, specific GBS treatment is usually not necessary during labor. However, GBS status can change, and certain risk factors, such as preterm labor, fever during labor, or prolonged rupture of membranes, may still warrant antibiotic administration even with a prior negative result. Consulting with a healthcare provider to discuss test results and any potential next steps is important for appropriate management.