You went in for a routine pregnancy check-up, got a swab you barely noticed, and now your chart says you tested positive for group B strep. Suddenly you're picturing the worst. Take a breath. Testing positive for group B strep is extremely common, it does not mean anything is wrong with you or your baby, and there is a simple, well-proven plan to keep your newborn safe.
Group B strep (GBS) lives quietly in many healthy adults. Here's what it actually is, why your provider screens for it late in pregnancy, and what happens next if your test comes back positive.
What is group B strep?
Group B strep is a type of bacteria, Streptococcus agalactiae, that naturally lives in the digestive tract and the vaginal and rectal area of many healthy people. In adults, it usually causes no symptoms at all. Carrying it is called being colonized, and it is not a sexually transmitted infection or a sign of poor hygiene.
About 1 in 4 pregnant women (roughly 25%) test positive for GBS during routine late-pregnancy screening, and most have no idea they carry it. Globally, maternal colonization ranges from about 10% to 40%, with a mean prevalence around 18%. The concern isn't the mother's health, it's that the bacteria can pass to a baby around the time of birth.
Why group B strep matters for newborns
GBS is a leading cause of bloodstream infections (sepsis), pneumonia, and meningitis in newborns. A baby can be exposed during a vaginal delivery through contact with fluids that contain the bacteria.
The reassuring part: most babies born to colonized mothers stay perfectly healthy. Vertical transmission happens in roughly 50% to 70% of babies born to colonized mothers, and of those, only about 1% to 2% develop early-onset invasive disease. Still, because newborn infections can become serious quickly, the goal is to prevent them entirely.
- Early-onset disease appears in the first week of life and shows up as sepsis, pneumonia, or meningitis.
- Late-onset disease appears later, between 7 and 90 days of life.
- Before active prevention efforts, an estimated 7,500 cases of neonatal GBS disease occurred each year in the United States.
How group B strep testing works
The CDC recommends universal screening for every pregnancy, late in pregnancy at about 35 to 37 weeks of gestation. The test is quick and painless: a provider rubs a sterile swab on the vagina and rectum, then sends it to a lab to check for the bacteria.
Because GBS can come and go, the test is timed close to delivery so the result reflects your status at birth. A positive result simply means you are colonized at that moment. There is nothing you did to cause it and no over-the-counter product that reliably clears it before labor.
What treatment looks like if you test positive
If your screening is positive, the standard plan is antibiotics given through an IV during labor, not weeks earlier. This is called intrapartum antibiotic prophylaxis, and it is timed to protect the baby during delivery.
The protection is striking. With antibiotics during labor, a newborn's chance of GBS disease drops to about 1 in 4,000, compared with about 1 in 200 without them. Penicillin is the typical first choice; if you have a penicillin allergy, your care team will choose an alternative, so always tell them about any drug allergies. This is general education, not a personal prescription, and your obstetric team will tailor the plan to you.
When to call your doctor
Group B strep itself rarely causes symptoms in pregnant adults, so the most important step is keeping your prenatal appointments and making sure your GBS result is on your delivery chart. Bring your status with you when you go into labor, especially if you deliver somewhere other than your usual hospital.
Reach out to your provider promptly, or seek urgent care, if any of the following apply.
- Your water breaks early or you go into labor before your scheduled GBS screening.
- You develop a fever during labor.
- In the first three months after birth, your baby is feeding poorly, unusually sleepy or hard to wake, breathing fast or with difficulty, running a fever, or seems limp or very irritable, which can be warning signs of newborn infection and need emergency evaluation.
Medical Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider before starting any new skincare treatment, especially if you have underlying health conditions, are pregnant, or are taking medications.
