Group B Strep (GBS) and Pregnancy: What You Need to Know
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What is Group B Strep?
Group B Streptococcus (GBS) is a type of bacteria found in the vagina or rectum of approximately 25% of healthy pregnant individuals. It does not cause illness in most adults but can harm newborns, who lack natural immunity [1]. Screening occurs in the third trimester, and positive results are managed with IV antibiotics during labor for a safe delivery [1] [2].
Key Takeaways
Bacterial cause: *Streptococcus agalactiae*, naturally occurring in about 25% of adults [1].
Screening window: Routinely performed between 36 and 37 weeks of pregnancy [1].
Transmission: Passed from mother to baby during vaginal childbirth.
Prevention: Intravenous (IV) antibiotics (e.g., penicillin) during labor [1] [2].
Infant risks: Sepsis, pneumonia, and meningitis (if untreated) [1].
Adult symptoms: Usually none; GBS is not an STI and is not related to hygiene [1].
What the research says
Colonization and transmission: A 2026 meta-analysis of 116 studies (53,770 participants) from 29 African countries found a pooled maternal rectovaginal GBS colonization prevalence of 18% and a pooled vertical transmission proportion of 47%. Resistance to the β-lactams ampicillin (10%) and penicillin (9%) was low [4].
Prevention works: A 2026 meta-analysis of 19 observational studies (3,707,047 women) notes that early-onset GBS disease remains a leading cause of neonatal illness and death, and that its incidence can be substantially reduced by intrapartum antibiotic prophylaxis in women with defined risk factors. It also found a modest association between higher pre-pregnancy BMI and early-onset GBS risk (odds ratio 1.4 at a BMI of 35 compared with a normal BMI) [3].
Understanding Group B Streptococcus
Group B streptococcus (GBS) is a bacterium that typically lives in the intestines, vagina, and rectum. For most healthy adults, GBS does not cause any health problems or symptoms. It is not a sexually transmitted infection (STI), nor is it a result of poor hygiene. It is a naturally occurring part of the body's microbiome for many people [1]. It is different from Group A strep, which causes strep throat.
The primary concern arises during pregnancy and childbirth. Because newborns have not yet developed a robust immune system, they are highly susceptible to the bacteria if exposed during a vaginal delivery [1].
Screening and Diagnosis
To protect infant health, healthcare providers use universal GBS screening for pregnant individuals. The test is typically done during the third trimester, between weeks 36 and 37 [1] [2].
The screening process is quick and painless:
The swab: A healthcare provider uses a sterile cotton swab to collect samples from the vagina and rectum [1].
Laboratory analysis: The sample is sent to a lab to check for GBS bacteria.
Results: Most patients receive results within about 48 hours [1]. A positive result means the bacteria are present; it does not mean the mother or baby is currently sick.
Symptoms and Risks for Newborns
While adults rarely show symptoms, GBS can cause serious complications in infants. They are grouped by the timing of onset:
Common symptoms in newborns
If left untreated, GBS can lead to life-threatening conditions such as sepsis (blood infection), pneumonia (lung infection), or meningitis (inflammation of the brain and spinal cord lining) [1]. Most infants recover fully, but meningitis can sometimes lead to long-term problems such as hearing loss, learning disorders, or seizures [1].
Management and Prevention Strategies
The most effective way to prevent GBS transmission is IV antibiotics during labor [2]. See also our guide to the stages of labor.
IV antibiotics: Penicillin or ampicillin are the most common choices, given through an IV once labor begins or the water breaks [1] [2]. If you have a penicillin allergy, your doctor will use an alternative [2].
Timing is critical: Antibiotics work best when given at least four hours before the baby is born [1].
Special cases: If GBS is found in the urine earlier in pregnancy, oral antibiotics may be prescribed right away, followed by IV treatment during labor [1]. GBS can also cause urinary tract infections in pregnancy.
C-section deliveries: Antibiotics are generally not required for scheduled C-sections if the water has not broken and labor has not started [1].
With proper antibiotic treatment, the risk of a baby developing a GBS infection drops significantly, from about 1 in 200 to about 1 in 4,000 [1] [2]. GBS is also a consideration in preterm labor and in infections such as chorioamnionitis; for another infection to be aware of in pregnancy, see listeria in pregnancy.
Conclusion
Testing positive for Group B Strep is common in pregnancy and is not a cause for alarm. By taking part in routine screening and receiving appropriate antibiotic care during delivery, parents can effectively protect their newborns from the risks associated with GBS. Open communication with your healthcare team makes sure the right preventive measures are in place for a safe and healthy arrival.
For more visual health resources and guides, explore our Rinnit Infographic Templates.
FAQ: Frequently Asked Questions
What is Group B Strep?
It is a common bacterium that lives naturally in the body.
Is GBS an STI?
No, it is not a sexually transmitted infection.
How do I get GBS?
It is naturally occurring; it is not caught from others or caused by poor hygiene.
Is GBS dangerous for adults?
Usually no, unless the person is immunocompromised.
When am I tested for GBS?
Between 36 and 37 weeks of pregnancy.
How is the test performed?
With a quick swab of the vagina and rectum.
Does the GBS test hurt?
No, it is a painless procedure.
What does a positive result mean?
It means you carry the bacteria, not that you are sick.
How common is GBS?
About 1 in 4 pregnant individuals test positive.
How is GBS treated?
With IV antibiotics during labor.
What is the best antibiotic for GBS?
Penicillin or ampicillin are most common.
Can I take oral antibiotics instead?
IV antibiotics are necessary during labor for effective prevention.
Why do I need antibiotics during labor?
To prevent passing the bacteria to the baby during delivery.
What if I'm allergic to penicillin?
Your doctor will use an alternative effective antibiotic.
Does a positive test mean I need a C-section?
No, GBS does not change the method of delivery.
Do I need antibiotics if I have a C-section?
Usually not, unless labor starts or your water breaks first.
What are the risks to the baby?
Sepsis, pneumonia, and meningitis.
What is early-onset GBS?
Infection appearing in the first few days of life.
What is late-onset GBS?
Infection appearing 7 days to 3 months after birth.
Can GBS be prevented?
Transmission to the baby can almost always be prevented with antibiotics during labor.
What are the signs of GBS in a newborn?
Fever, grunting, lethargy, and poor feeding.
How is a newborn treated for GBS?
With IV antibiotics in the hospital.
Can I pass GBS to my other children?
No, it is not spread through normal contact.
Does GBS go away after pregnancy?
It may remain as part of your natural bacteria.
What if my water breaks early?
You will likely start antibiotics immediately if you are GBS positive.
Is the GBS test mandatory?
It is highly recommended as a standard of prenatal care.
How long do lab results take?
Usually about 24 to 48 hours.
What if I haven't been tested when I go into labor?
You will likely receive antibiotics as a precaution.
Does GBS affect breastfeeding?
No, you can safely breastfeed if you are GBS positive.
Can GBS cause a UTI?
Yes, GBS can sometimes cause urinary tract infections in pregnancy.
What if I had GBS in a previous pregnancy?
You will be tested again, as status can change.
What if my previous baby had GBS?
You will automatically receive antibiotics during this labor.
Does GBS cause a fever in the mother?
Usually not, unless it causes a specific infection like a UTI.
How effective are the antibiotics?
They greatly reduce the risk of infant infection, from about 1 in 200 to about 1 in 4,000.
Can I get GBS from a swimming pool?
No, it is not spread through water.
Is GBS the same as strep throat?
No, strep throat is caused by Group A Streptococcus.
Can GBS cause premature labor?
It is a recognized risk factor for preterm birth.
How long do the IV antibiotics take?
They are given every few hours until delivery.
What is sepsis?
A serious blood infection caused by the body's response to bacteria.
What is meningitis?
An infection of the lining of the brain and spinal cord.
Can GBS cause long-term hearing loss?
It is a possible complication of GBS meningitis.
Is GBS related to diet?
No, it is not caused by what you eat.
Can I use a vaginal wash to clear GBS?
No, washes are not effective at removing GBS.
Should my partner be tested?
No, GBS is not treated as a contagious infection between partners.
What if I test negative but have risk factors?
GBS antibiotics are usually not needed after a negative test, even if labor is long; they are given when your GBS status is unknown and risks such as preterm labor, fever or water broken for 18 hours or more are present.
Does GBS affect the baby's development in the womb?
Usually not; the risk is primarily during delivery.
Can late-onset GBS be prevented by labor antibiotics?
Labor antibiotics primarily prevent early-onset GBS.
Is GBS common worldwide?
Yes, it is a globally recognized concern in neonatal health.
Related Reading
Urine Culture: How the Test Works, How to Collect a Sample and What Results Mean explains how a urine culture confirms a UTI and guides antibiotic choice.
References
Cleveland Clinic. Group B Strep Pregnancy. Cleveland Clinic. Last updated August 27, 2025. https://my.clevelandclinic.org/health/diseases/group-b-strep
Centers for Disease Control and Prevention. Preventing Group B Strep Disease in Newborns. CDC. Last updated May 1, 2025. https://www.cdc.gov/group-b-strep/prevention/index.html
Graae EE, Uldbjerg N, Skjøth F, et al. Maternal body mass index and the risk of early-onset Group B Streptococcus disease in newborns: a systematic review and meta-analysis. PLoS One. 2026;21(5):e0329423. PMID 42102051. https://doi.org/10.1371/journal.pone.0329423
Melaku T, Mekonnen Z, Abebe G, et al. Group B Streptococcus in African pregnancies: a systematic review and meta-analysis of its maternal rectovaginal colonization, vertical transmission, serotype distribution, and antimicrobial resistance. Int J Infect Dis. 2026;170:108702. PMID 42001933. https://doi.org/10.1016/j.ijid.2026.108702
Medical Disclaimer
The information provided in this article is for educational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional for prenatal care and delivery planning.
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