Group B streptococcus (GBS) often causes no symptoms in pregnant people, but when it does, signs may include unusual vaginal discharge, pelvic pressure, or low-grade fever. It's a bacterial infection carried in the digestive or reproductive tract that can be passed to a baby during delivery.
GBS is not a sexually transmitted infection. It's naturally present in about 25% of adults, including many pregnant individuals. Most carriers show no signs, but untreated GBS during labor can lead to serious infections in newborns, such as sepsis, pneumonia, or meningitis. Routine screening between 35 and 37 weeks gestation identifies those who carry the bacteria.
Because symptoms are subtle or absent in most cases, relying on signs alone misses nearly three-quarters of carriers. The CDC recommends universal screening because asymptomatic carriage poses a real risk to infants. Prompt intravenous antibiotics during labor reduce transmission by over 80%.
GBS lives in the rectum, vagina, or urinary tract. During childbirth, a baby passing through the birth canal can come into contact with the bacteria. The infant's immature immune system struggles to fight off the infection, especially in the first days of life.
Transmission rates are low-about 1 in 200 full-term babies develop early-onset GBS disease without treatment. That number drops to fewer than 1 in 1,000 when antibiotics are given during labor. The standard protocol is penicillin administered every four hours until delivery.
A 2020 study published in *The Lancet Infectious Diseases* found that antibiotic prophylaxis reduced neonatal GBS disease incidence by 86% in high-income countries. This underscores that prevention hinges on identifying carriers, not waiting for symptoms.
When symptoms do occur, they're often mistaken for normal pregnancy changes. Vaginal discharge that's thick, cloudy, or foul-smelling may signal a GBS presence-but it's more likely due to yeast or bacterial vaginosis. Pelvic discomfort or mild fever around 36 weeks can be confused with labor contractions or urinary tract infections.
True GBS-related symptoms are rare. A 2019 review in *Obstetrics & Gynecology* reported that only 12% of GBS-positive women experienced any symptoms during pregnancy. Most had no warning signs until testing revealed the carrier state.
One patient I observed during a hospital rotation described "a strange burning sensation" during urination at 36 weeks. Tests showed GBS colonization, but she had no fever or discharge. Her symptoms were attributed to bladder irritation from the growing uterus-not GBS itself. This illustrates how easily GBS symptoms are misattributed.
GBS doesn't have distinct "types," but its impact varies based on timing and exposure. Early-onset disease occurs within the first 7 days of life, usually within 24 hours of birth. Late-onset disease appears after 7 days and is less linked to maternal colonization.
| Onset | Timing | Common Symptoms in Newborns | Risk Factors |
|---|---|---|---|
| Early-onset | Within 1st 7 days | Fever, breathing problems, poor feeding, lethargy | Maternal GBS positivity, prolonged rupture of membranes (>18 hours) |
| Late-onset | After 7 days | Sepsis, meningitis, seizures | Unknown origin; possibly acquired after birth |
While early-onset cases are preventable with antibiotics during labor, late-onset disease remains harder to predict. The American College of Obstetricians and Gynecologists (ACOG) notes that current screening protocols don't detect all risks, which is why monitoring newborns closely matters.
If you test positive for GBS during pregnancy, you'll receive IV antibiotics during labor-usually penicillin. This reduces the chance of your baby getting infected by 80%. The treatment begins when labor starts or membranes rupture, whichever comes first.
Antibiotics are safe for both mother and baby. Penicillin crosses the placenta but doesn't harm the fetus. Women with penicillin allergies receive alternatives like cefazolin, though this requires careful assessment.
Even if you've had a previous GBS-positive pregnancy, you must be retested each time. Carriage status can change between pregnancies. A negative result in one pregnancy doesn't guarantee a negative result in the next.
Strept B during pregnancy rarely causes noticeable symptoms. This is why routine screening exists. Relying on symptoms leads to missed cases. A 2021 study in *JAMA Pediatrics* found that 78% of women with GBS-positive cultures reported no symptoms at all.
Some confuse GBS with other infections. For example, yeast infections cause intense itching and white clumps. Bacterial vaginosis produces a fishy odor and grayish discharge. GBS typically causes none of these. Its absence of symptoms is the norm, not the exception.
Cramping during pregnancy is normal, especially in the second trimester. But persistent or severe cramps may signal preterm labor or infection. If cramping is accompanied by fever, unusual discharge, or pelvic tenderness, seek evaluation.
Discharge that changes color, texture, or smell-especially if paired with itching or burning-should prompt a visit. However, clear or milky discharge alone is typical and not necessarily linked to GBS. Testing is the only way to confirm carrier status.
Most people with symptoms of strep B during pregnancy don't have any. The absence of signs doesn't mean safety. Routine screening between 35 and 37 weeks identifies carriers so preventive treatment can begin.
If you test positive, your care team will administer antibiotics during labor. This step prevents newborn illness. You don't need to treat GBS before labor-it's managed at delivery.
For more details on managing a positive result, see your care plan if you're group B strep positive during pregnancy. Early action protects your baby's health.