Group B streptococcus - pregnancy

Most of the time, GBS is harmless. However, GBS can be passed to a newborn during birth.

Most babies who come in contact with GBS during birth will not become sick. But the few babies who do become ill can have severe problems.

After your baby is born, GBS can lead to infections in:

• The blood (sepsis)
• The lungs (pneumonia)
• The brain (meningitis)

Most babies who get GBS will start having problems during their first week of life. Some babies will not get sick until later. Symptoms can take as long as 3 months to appear.

The infections caused by GBS are serious and can be fatal. Yet prompt treatment usually leads to complete recovery.

Women who carry GBS often don't know it. You are more likely to pass the GBS bacteria to your baby if:

• You go into labor before week 37.
• Your water breaks before week 37.
• It has been 18 or more hours since your water broke, but you haven't had your baby yet.
• You have a fever of 100.4°F (38°C) or more during labor.
• You have had a baby with GBS during another pregnancy.
• You have had urinary tract infections that were caused by GBS.

When you are 35 to 37 weeks pregnant, your health care provider may do a test for GBS. Your provider will take a culture by swabbing the outer part of your vagina and rectum. The swab will be tested for GBS. Results are often ready in a few days.

Some providers do not test for GBS. Instead, they will treat any woman who is at risk for having their baby be affected by GBS.

There is no vaccine to protect women and babies from GBS.

If a test shows that you carry GBS, your provider will give you antibiotics through an IV during your labor. Even if you are not tested for GBS but have risk factors, your provider will give you the same treatment.

There is no way to avoid getting GBS.

• The bacteria are widespread. People who carry GBS often have no symptoms. GBS can come and go.
• Testing positive for GBS does not mean you will have it forever. But you will still be considered a carrier for the rest of your life.

Note: Strep throat is caused by a different bacterium. If you have had strep throat, or got it while you were pregnant, it does not mean that you have GBS.

GBS - pregnancy

Duff WP. Maternal and perinatal infection in pregnancy: bacterial. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Philadelphia, PA: Elsevier; 2021:chap 58.

Mukherjee D, Ryan RM. Postnatal bacterial infections. In: Martin RJ, Fanaroff AA, eds. Fanaroff and Martin's Neonatal-Perinatal Medicine. 12th ed. Philadelphia, PA: Elsevier; 2025:chap 50.

Pannaraj PS, Baker CJ. Group B streptococcal infections. In: Cherry J, Harrison GJ, Kaplan SL, Steinbach WJ, Hotez PJ, eds. Feigin and Cherry's Textbook of Pediatric Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier; 2019:chap 83.

Verani JR, McGee L, Schrag SJ; Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention (CDC). Prevention of perinatal group B streptococcal disease--revised guidelines from CDC, 2010. MMWR Recomm Rep. 2010;59(RR-10):1-36. PMID: 21088663 pubmed.ncbi.nlm.nih.gov/21088663/.

Updated by: John D. Jacobson, MD, Professor Emeritus, Department of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.