Group B Streptococcus, or GBS, is a common bacteria found in the digestive and lower genital tracts of many healthy adults. Most people who carry it never know, because it causes no symptoms and poses no risk to the carrier. In pregnancy, the concern shifts. GBS can transfer to the baby during delivery, which is why a simple swab test is part of routine late prenatal care. A positive result is not a cause for alarm. It is manageable, well-understood and handled with a straightforward protocol during labor.
What Is Group B Strep?
Group B Strep is a gram-positive bacterium found naturally in the gastrointestinal and genitourinary tracts of roughly 10 to 30 percent of adults. It is not a sexually transmitted infection and is not related to Group A Strep, the bacteria responsible for strep throat. Most people who carry GBS have no idea, because it produces no odor, discharge, irritation or other noticeable signs.
GBS is considered a commensal organism in adults, meaning it coexists in the body without causing harm. The immune systems of healthy adults manage it on their own. Pregnancy changes that picture in one specific way: during vaginal delivery, the baby passes through a birth canal where GBS may be present, and a newborn’s immune system is not yet equipped to handle the bacteria the way an adult’s is. That narrow window of exposure during delivery is the reason screening exists.
GBS status can also change between pregnancies and even within a single pregnancy. A negative result in a previous pregnancy does not predict what will happen in the current one, which is why providers test during every pregnancy regardless of past results.
When and How Is the Group B Strep Test Done?
The GBS screening swab is performed between weeks 35 and 37 of pregnancy during a routine prenatal visit. At this point in the pregnancy, the result reflects the most current bacterial status, which is what matters for labor management.
The swab itself takes only a few seconds. A soft cotton swab is used to collect a sample from the lower vagina and the rectum. No speculum is involved and the swab does not enter the cervix. Most patients describe it as comparable to any other routine pelvic swab. In some practices, patients are given the option to perform the swab themselves in a private space with provider guidance, which some find more comfortable.
The sample is sent to a laboratory, and results are typically available within 24 to 48 hours. Your provider will review the result at your next visit, or reach out sooner if the finding calls for any changes to your care plan.
What if Labor Starts Before the Test?
If labor begins before the GBS swab has been completed, the standard approach is to treat the patient as though she were GBS-positive until a rapid test or clinical picture indicates otherwise. Most hospitals can run a rapid GBS test in this scenario, though results are not always available before delivery. Defaulting to antibiotic coverage protects the baby in the absence of confirmed status, and the antibiotic used carries a very low risk profile in otherwise healthy patients. Letting your provider know you have not yet been tested when you arrive at the hospital helps the labor team make that call quickly.
What Does a Positive GBS Result Mean?
A positive GBS result means the bacteria is currently present in the vaginal or rectal area. It does not mean you are ill, that something went wrong, or that your pregnancy is now considered high-risk. It is simply information your provider needs to adjust one part of your labor plan.
The standard response to a positive GBS result is intravenous antibiotics administered at the start of active labor. Penicillin is the first-line treatment and is highly effective at reducing the amount of GBS present in the birth canal during delivery. For patients with a penicillin allergy, alternative antibiotics are available, and your provider will identify the appropriate option well before your due date based on your allergy history and any sensitivity testing from the culture. For more on vaccines and antibiotic treatments used during pregnancy, visit the pregnancy and vaccines page.
Timing matters. Antibiotics are most effective when given at least four hours before the baby is born, which is why your provider will want to start the IV as soon as labor is confirmed. If you arrive at the hospital close to delivery, your team will still administer antibiotics, though the protective effect may be reduced. This is one reason knowing your GBS status in advance is useful, as it allows the labor team to act quickly without waiting for results.
Can I Still Have a Natural or Unmedicated Birth?
A GBS-positive result does not require any specific type of delivery or rule out an unmedicated birth. The IV antibiotic is typically given over a 15 to 30-minute infusion and does not need to remain attached throughout labor. Many patients receive the antibiotics, are unhooked from the IV line and continue laboring without further interference. Your birth plan remains largely intact. Discussing your preferences with your provider before labor begins means the team can time the antibiotic administration around your plan rather than around a fixed schedule. For more on how to prepare, read our post on what to do to prepare for your baby’s delivery.
How Is the Baby Monitored After Delivery?
After delivery, the focus shifts to the baby. Newborns born to GBS-positive mothers are observed closely in the hours that follow. The care team watches for early signs of GBS infection, which can include fever, breathing difficulty, poor feeding and unusual fussiness. Babies born to GBS-positive mothers who received antibiotics during labor typically show no signs of infection and are discharged on the normal postpartum timeline. Routine observation typically means a pediatric check within the first few hours rather than any additional procedures or extended hospital stay.
Early-onset GBS disease in newborns, which develops within the first week of life, is the complication that intrapartum antibiotic prophylaxis is designed to prevent. When that four-hour window is met, the rate of early-onset GBS disease in newborns drops significantly. Late-onset GBS disease, which appears between one week and three months of age, is not prevented by labor antibiotics and can occur regardless of the mother’s GBS status, often from community or household exposure after birth.
If you notice any signs of illness in your newborn in the days or weeks after discharge, contact your pediatrician promptly. Early-onset infections can progress quickly in newborns, and early treatment is highly effective.
Talk to Your Provider About Group B Strep at Roswell Ob/Gyn, LLC
A positive GBS result is one of the most manageable findings in late pregnancy, and knowing your status ahead of labor means your care team can act immediately when delivery begins. Roswell Ob/Gyn, LLC performs GBS screening as part of routine prenatal care across locations in Alpharetta, Atlanta, Canton and Cumming, Georgia. Contact us to schedule your appointment.
Frequently Asked Questions
Does GBS affect how I deliver my baby?
GBS status alone does not determine your delivery method. Patients who test positive can still plan for a vaginal birth, and the labor experience itself does not change in any significant way. The only required adjustment is the IV antibiotic during labor. A cesarean delivery is not indicated based on GBS status unless other clinical factors are present.
Will I test positive for GBS every pregnancy?
Not necessarily. GBS colonization is transient, meaning it comes and goes. Prior negative results do not carry forward, and status can shift in either direction between or even during pregnancies. Testing is repeated each pregnancy because status can change.
What if I test negative but develop a GBS urinary tract infection during pregnancy?
GBS can also be detected through a urine culture earlier in pregnancy. If GBS is found in the urine at any point, it is treated immediately with oral antibiotics, and IV antibiotics during labor are automatically recommended regardless of the late-pregnancy swab result. Read more about how to spot signs of a UTI and when to see an OB/GYN.
Can GBS affect my pregnancy before labor?
In most cases, vaginal GBS colonization does not cause complications during pregnancy itself. GBS found in urine is a different concern and is treated promptly because urinary tract infections during pregnancy carry a risk of preterm labor. Routine vaginal GBS colonization, by contrast, is monitored rather than treated until labor begins.
Is GBS testing optional?
GBS testing is a standard recommendation from major obstetric organizations including ACOG, but it is not legally mandated. Some patients decline testing for personal reasons. If you choose not to test or if results are unavailable at delivery, your provider will discuss risk-based management, which may include prophylactic antibiotics during labor depending on your clinical history.
Can I reduce my chances of testing positive for GBS?
There is no clinically proven method to prevent GBS colonization. Probiotics, dietary changes and vaginal washes are sometimes discussed in patient forums, but none have sufficient evidence to be recommended as preventive measures. If you have concerns about GBS, the most reliable step is attending your scheduled prenatal appointments and completing the swab at weeks 35 to 37.
