Understanding Group B Streptococcus

What is Group B Strep?

Group B Streptococcus (GBS), or beta strep, is a normal bacterium commonly found in the intestinal tract along with other healthy bacteria.  It is a transient bacterial colonization present intermittently throughout a woman's life.  When present during pregnancy, women should more accurately be termed "GBS colonized" rather than "GBS infected", as its presence in the intestinal tract is normal.

Screening and Diagnosis

The American College of Obstetricians and Gynecologists (ACOG) and the US Centers for Disease Control and Prevention (CDC) recommend that all pregnant women be screened between 35 and 37 weeks to determine if they are carriers of GBS by taking a swab of the vaginal and rectal areas. About 30% of pregnant women are found to be colonized with GBS in one or both areas.

GBS can cause problems, such as sepsis (a blood infection), pneumonia, and/or meningitis (an infection of the fluid and lining of the brain), when it is transmitted from the mother to the baby, usually during labor. However, research has shown GBS can also be transmitted prenatally across the amniotic membranes, sometimes through invasive procedures such as cervical exams, membrane stripping, internal fetal monitoring or during the application of cervical ripeners for induction. When any of these conditions occur, there is a small risk that the bacteria will be passed to the baby, causing it to become sick.

There are two recognized forms of Group B Streptococcus infection: early and late onset. A third type, prenatal onset, occurs when the bacteria crosses the amniotic membranes prenatally and can result in early or late pregnancy miscarriage or stillbirth. It is not yet known how many babies are affected in this manner.

Of these, the most prevalent form is early onset. In early-onset GBS disease, babies will become ill within seven days of birth.  In severe early-onset GBS infection, about 6 percent of babies will die from complications of the infection. Full-term babies are less likely to die; 2-8% suffer fatal complications. Premature babies have mortality rates of 25-30%.  Late-onset GBS infection is more complicated and may not be related to the mother's GBS status.  It occurs between seven days and three months of age.

Symptoms of early-onset Group B Streptococcus infection include any of the following: fever or abnormally low body temperature, jaundice (yellowing of the skin and whites of the eyes), poor feeding, vomiting, seizures, difficulty in breathing, swelling of the abdomen, and bloody stools. The most common symptom is difficulty breathing, which is also the most common complication in babies whose mothers chose drugs during labor.  Since these symptoms can occur in so many circumstances unrelated to GBS, a C-Reactive protein test can be given to a symptomatic baby to reveal the presence of an active infection.

Risk Factors for GBS Disease

There are three significant factors that place babies at increased risk of infection: fever during labor, water breaking 18 hours or more before birth (prolonged rupture of membranes, or PROM), and/or labor or broken water before 37 weeks.  Other factors that can contribute to a newborn's risk of contracting Group B Streptococcus infection include age, ethnicity, and medical criteria, such as the following: being born to a mother who is less than 20 years old, being African American, a high colonization of GBS bacteria, and having had a previous baby with GBS disease.

Recommended Treatment

The recommended treatment by the CDC and ACOG is intravenous antibiotics during labor for all women who swab positive during their pregnancies without regard to the concentration of colonization present. While this practice has been successful in reducing the rate of early-onset infection from 0.7 cases per 1000 live births in the U.S. in 1997 to 0.32 cases per 1000 live births in the U.S. in 2004, it has not affected the number of babies who will die from early or late onset GBS disease. Furthermore, the use of intrapartum antibiotics has not been found to be evidence-based in a meta analysis conducted by the Cochrane Collaboration.

Two in 10,000 babies may be saved by antibiotics during birth, but this comes at the cost of giving 1/3 of all pregnant women antibiotics. There are many reasons women may not want antibiotics for Group B Streptococcus. These include:

    Increasing occurrence of antibiotic-resistant infections ("superbugs" such as MRSA - Methicillin-resistant Staphylococcus Aureus).
  • Use of antibiotics has increased risk of developing other life-threatening infections such as sepsis & E. Coli.
  • GBS+ status alone is a poor indicator of which babies will become ill.
  • Antibiotics fail to prevent infection in 30% of cases.

The most-commonly used antibiotic for treating Group B Streptococcus during labor is penicillin. Fewer bacteria currently show a resistance to penicillin than to other antibiotics used to treat GBS. It’s only a matter of time until penicillin is also ineffective against GBS.

If allergic to penicillin, options decrease.  29% of Group B Streptococcus strains are resistant to non-penicillin antibiotics.  There's a 1/10 chance of a mild reaction such as a rash, and a 1/10,000 chance of anaphylaxis, a life-threatening allergic reaction to penicillin, even for those who've taken it previously. Reactions can start or strengthen in severity during pregnancy.

Reducing Colonization

Even though Group B Streptococcus colonization is transient, without an active effort to eradicate the GBS colonization, it is likely that women will still be colonized after 37 weeks. The degree and location of colonization, especially if present in the mother's urine, which is not routinely tested, is a more reliable indicator of transmission risk. Unfortunately, these factors are not considered within the universal treatment protocol. Better outcomes can be attained by focusing on first reducing colonization rather than only treating it after the fact.

There are probiotic approaches that focus on restoring a healthy vaginal flora balance, reducing bacterial overgrowth, and directly reducing the bacterial concentration.   Alternative options focus on:

  • Reducing the vaginal colonization by correcting the vaginal pH
  • Boosting the overall immune system to further reduce vaginal colonization thereby increasing the antibodies passed to the baby, thus increasing the baby's immune response if exposed.

Unfortunately, limited research has been conducted on minimizing colonization, opting instead for intrapartum antibiotics after a positive culture despite the unfavorable research evidence.

Another option is to not screen for beta strep during pregnancy, but to follow a strict protocol during birthing if any of the following risk factors are present: 1) fever over 38 degrees Celsius, 2) pre-term birthing < 37 weeks, 3) prolonged rupture of membranes > 18 hours, 4) multiple births, and 5) previously-infected baby.  In these cases antibiotics may be indicated.  Those infants who are symptomatic (fever, fast breathing, poor feeding, high pitched cry) can be evaluated for sepsis and given antibiotics for 48-72 hours.  Alternately, a C-reactive protein test can be performed to determine the presence of an active infection before giving antibiotics to the baby.

Return to Top of Group B Streptococcus


    Breastfeed immediately and frequently. Colostrum is full of antibodies that strengthen the baby's immune system.
  • Refuse vaginal exams
  • Avoid internal fetal monitoring
  • Refuse membrane stripping or sweeping
  • Avoid induction of labor or application of cervical ripeners
  • Do not permit artificial rupture of membranes.

Sample Birth Plan Language

After assessing risk factors and deciding upon a plan of action, it can be added either in the body of a birth plan or as an addendum.  Here is sample language that may be included:

I (will/will not) be screened for Group B Streptococcus.

If the result is negative, the only precautions will be to closely monitor labor for the above risk factors and monitor the baby after childbirth for possible signs of infection.

If any of the risk factors (fever over 38 degrees Celsius, pre-term birthing < 37 weeks, prolonged rupture of membranes > 18 hours) occur, mother will consent to ___________.

If the result is positive the treatment of choice is :_______

Mother’s Signature                Date                            Care Provider‘s Signature                    Date


F. Smaill, "Intrapartum Antibiotics for Group B Streptococcal Colonization," Cochrane Database Syst Rev 2 (2000): CD000115: www.ncbi.nlm. nih.govl.

S. D. Manning et al., "Correlates of Antibiotic-Resistant Group B Streptococcus Isolated from Pregnant Women," Obstetric Gynecology 101, no. 1 (2003): 74-79

 R. K. Edwards et al., "Intrapartum Antibiotic Prophylaxis 2: Positive Predictive Value Antenatal Group B Streptococci Cultures and Antibiotic Susceptibility of Clinical Isolates," Obstetric Gynecology 100, no. 3 (2002): 540-544.

M. Dabrowska-Szponar and J. Galinski. "Drug Resistance of Group 9 Streptococci," Pol Merkuriusz Lek 10, no. 60(2001): 442-444.

M. L. Bland et al., "Antibiotic Resistance Patterns of Group B Streptococci in Late Third Trimester Rectovaginal Cultures," American Journal of Obstetric Gynecology 184. no, 6 (2001): 1125-1126.

T. B. Hyde ct al., "Trends in Incidence and Antimicrobial Resistance of Early-Onset Sepsis: Population-Based Surveillance in San Francisco and Atlanta," Pediatrics 110, no. 4 (2002): 690-695.

R. S. McDuffie Jr. et al., "Adverse Perinatal Outcome and Resistant Enterobacteriaceae after Antibiotic Usage for Premature Rupture of Membranes and Group B Streptococcus Carriage," Obstetric Gynecology 82, no. 4, pt. 1 (1993): 487-489.

C. V. Towers and G. G. Briggs, "Antepartum Use of Antibiotics and Early-Onset Neonatal Sepsis: The Next Four Years," American Journal of Obstetric Gynecology 187, no. 2 (2002): 495-500.

S. J. Schrag et al., "A Popular/on Based Comparison of Strategies Co Prevent Early-Onset Group B Streptococcal Disease in Neonates," New England Journal of Medicine 347 (2002): 233-239.

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Page Last Modified by Catherine Beier, MS, CBE

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