Testing GBS positive in pregnancy means you carry a common bacterium called Group B Streptococcus in your vagina or rectum. About 1 in 4 pregnant women carry GBS. It’s not a sexually transmitted infection and it doesn’t mean you’re sick. GBS is a normal part of many people’s bacterial flora, but it can pose a risk to your baby during a vaginal delivery if steps aren’t taken to manage it.
What GBS Actually Is
Group B Streptococcus is a type of bacteria that naturally lives in the digestive and reproductive tracts of many adults. In women, it’s most commonly found in the vagina and rectum. Carrying it doesn’t cause symptoms, and most people who have it never know unless they’re tested. It can come and go on its own, which is why the timing of your screening matters.
GBS is completely different from the strep that causes strep throat. That’s Group A Strep. Group B Strep rarely causes problems in healthy adults, but newborns have immature immune systems that can’t fight it off easily. The concern during pregnancy is that the baby can pick up the bacteria while passing through the birth canal.
How and When You’re Tested
GBS screening is a routine part of prenatal care, typically done between 36 and 37 weeks of pregnancy. Your provider uses a swab to collect a sample from your vagina and rectum. It’s quick and not painful, similar to a Pap smear but even simpler. The sample goes to a lab, and results usually come back within a day or two.
The test is done late in pregnancy because GBS colonization can fluctuate. A result from earlier in pregnancy wouldn’t reliably predict whether you’re carrying the bacteria at the time of delivery. If you tested negative at 36 weeks but go into labor many weeks later (for example, past your due date), your provider may discuss whether retesting is appropriate.
GBS can also show up in a routine urine culture earlier in pregnancy. If that happens, you’re considered GBS positive for the rest of the pregnancy and won’t need the late-pregnancy swab test. Finding GBS in urine typically indicates heavier colonization.
What It Means for Your Delivery
If you test positive, the standard approach is to receive antibiotics through an IV during labor. The antibiotics work by reducing the amount of bacteria present in the birth canal at the time your baby passes through. Ideally, you’ll receive at least one dose at least four hours before delivery to give the medication time to take full effect. Penicillin is the most commonly used option, with alternatives available if you have an allergy.
You won’t take oral antibiotics beforehand. Taking them during pregnancy to try to eliminate GBS doesn’t work because the bacteria typically return before delivery. The antibiotics are only effective when given during active labor, close to the time the baby is actually exposed.
Once you arrive at the hospital in labor, your provider will already know your GBS status from your prenatal records. The IV is started early and the antibiotics are given at regular intervals until the baby is born. This doesn’t restrict your movement significantly during labor, and it doesn’t change how your delivery proceeds otherwise.
Planned C-Sections Are Handled Differently
If you have a scheduled cesarean delivery before labor starts and your water hasn’t broken, you do not need GBS-specific antibiotics. The baby isn’t passing through the birth canal, so there’s no exposure to the bacteria. You’ll still receive the standard pre-surgical antibiotics that are given before any C-section, but those serve a different purpose.
The exception is if you go into labor before your scheduled C-section date, or if your water breaks early. In that situation, your provider will give you antibiotics that cover both GBS and the usual surgical infection prevention, often in a single dose or combination.
The Risk to Your Baby Without Treatment
Without antibiotics during labor, a GBS-positive mother has roughly a 1 to 2 percent chance of passing the infection to her baby. That number is relatively small, but the consequences of neonatal GBS infection can be serious. With IV antibiotics, the risk drops dramatically.
GBS infections in newborns fall into two categories. Early-onset disease occurs within the first week of life and can cause sepsis (a bloodstream infection), pneumonia, or meningitis. Late-onset disease appears between 7 and 89 days after birth, and while it can cause the same illnesses, meningitis is more common in this form. Signs to watch for in a newborn include fever, poor feeding, unusual sleepiness or irritability, difficulty breathing, and bluish or pale skin. Seizures or a bulging soft spot on the head can signal meningitis.
Globally, GBS contributes to more than 500,000 premature births and roughly 150,000 stillbirths and infant deaths each year, according to the World Health Organization. In countries with universal screening and antibiotic treatment during labor, early-onset disease rates have dropped significantly over the past two decades.
Risks to the Mother
GBS colonization alone doesn’t harm you, but the bacteria is recognized as a risk factor for intraamniotic infection, sometimes called chorioamnionitis. This is an infection of the amniotic fluid and membranes surrounding the baby, and it’s more likely when labor is prolonged or when membranes have been ruptured for an extended time. Complications from intraamniotic infection can include prolonged or dysfunctional labor, postpartum hemorrhage, uterine infection after delivery, and in rare cases, sepsis. The antibiotics given during labor for GBS also help reduce these maternal risks.
What Happens After Delivery
If you received antibiotics at least four hours before delivery, your baby will typically be monitored with routine newborn observation. No additional testing is usually needed. If antibiotics were started less than four hours before birth, or if you didn’t receive them at all, your baby’s medical team will monitor more closely for signs of infection, usually for 24 to 48 hours. This may mean a slightly longer hospital stay, but most babies in this situation remain perfectly healthy.
A positive GBS result in one pregnancy doesn’t necessarily mean you’ll be positive in the next. Because colonization fluctuates, you’ll be screened again in each subsequent pregnancy. There’s nothing you can do between pregnancies to prevent GBS colonization. It’s not related to hygiene, diet, or lifestyle. It’s simply part of normal bacterial variation among adults.