Group B Streptococcus (GBS) is a common bacterium that frequently lives harmlessly in the gastrointestinal tract and can colonize the lower genital tract. This colonization, which occurs in an estimated 10% to 30% of healthy adult women, is considered a normal carriage state rather than an infection. Because GBS rarely causes symptoms in healthy adults, its presence is usually silent and does not produce noticeable changes in vaginal secretions. The reality is that GBS discharge is typically non-existent.
The Reality of GBS and Vaginal Discharge
GBS colonization usually results in no change from a person’s normal, healthy vaginal discharge. GBS is generally asymptomatic, meaning it exists within the body without causing signs of illness or irritation. Normal vaginal discharge is typically clear, white, or off-white, with a thin to milky consistency and a mild odor. If a person colonized with GBS does notice discharge, it is often non-specific and indistinguishable from physiological discharge, which naturally changes throughout the menstrual cycle. The bacteria do not typically trigger the inflammatory response necessary to produce the thick, malodorous, or highly discolored discharge associated with active vaginal infections.
Differentiating GBS from Other Causes of Abnormal Discharge
If a person experiences truly abnormal discharge, GBS is highly unlikely to be the sole cause; such symptoms usually point toward a different issue requiring medical evaluation. For example, a vaginal yeast infection produces a distinct discharge that is usually thick, white, and clumpy, often compared to cottage cheese, accompanied by pronounced itching and burning. Bacterial Vaginosis (BV) results from an imbalance in the vaginal flora, causing thin, grayish-white discharge with a strong, unpleasant “fishy” odor. Trichomoniasis, a sexually transmitted infection, causes a third distinct type of discharge, which can be thin and frothy, ranging in color from yellowish-green to gray, and may also have a foul odor. Since GBS colonization rarely causes these classic symptoms, any presentation of truly abnormal discharge suggests a co-existing infection that needs specific treatment.
Why Visual Symptoms Do Not Confirm a GBS Diagnosis
Relying on the appearance of vaginal discharge is an unreliable method for detecting Group B Strep colonization. Because GBS usually causes no noticeable symptoms, a person with completely normal discharge can still be a carrier. GBS is not diagnosed by visual inspection; it requires laboratory confirmation because it is a colonization, not an infection. The definitive diagnosis is achieved through a specific culture or polymerase chain reaction (PCR) test. This process involves collecting a swab sample from both the lower vagina and the rectum, which is then sent to a laboratory for analysis to confirm the presence of Streptococcus agalactiae.
Clinical Significance of GBS During Pregnancy
The primary focus of GBS testing relates to the risk it poses to newborns during vaginal birth. If a pregnant person is colonized, the bacteria can be passed to the baby, potentially leading to serious complications, including sepsis, pneumonia, or meningitis. Screening is typically performed late in pregnancy, between 36 and 37 weeks gestation, using the vaginal and rectal swab method. If the test returns positive, the standard protocol is to administer intravenous (IV) antibiotics during labor to reduce transmission risk. If GBS is detected in a urine culture at any point during the pregnancy, intrapartum antibiotic treatment is automatically recommended, regardless of the third-trimester swab result.