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Group B Streptococcus During Pregnancy.



Group B streptococcus, also referred to as “GBS,” is a bacterium that is often found in the vagina or rectum of expectant mothers. Although commonly misunderstood, GBS is not a sexually transmitted infection and usually does not cause symptoms in the mother. As many as thirty percent of pregnant patients may intermittently carry GBS during their pregnancy. However, since GBS is the most frequent cause of serious infections during a newborn’s first week of life, this bacterium has received a great deal of attention.

In 1996, with revisions in 2002 and 2010, the Centers of Disease Control released recommendations for preventing GBS infections during labor. These guidelines encourage screening of pregnant patients for the presence of GBS colonization with vaginal and rectal cultures between 35 and 37 weeks gestation. If these cultures are positive for GBS, antibiotic therapy is recommended during labor to minimize the chance of newborn infection.

If a patient has a urine culture that is positive for GBS at any time during her pregnancy or if a patient has had a prior newborn affected by a severe GBS infection, she does not need to obtain third trimester GBS cultures. In these two scenarios, the CDC has recommended that these patients be treated with antibiotics while in labor since their risks of newborn infection are higher. The prevention of GBS infection focuses on a mother delivering vaginally. Accordingly, patients scheduled for a cesarean section delivery do not require GBS cultures.

What if I do not know my GBS status when I go into labor?

If a patient’s GBS culture result is not available at the time of labor, the 2010 CDC guidelines recommend performing a test called a Nucleic Acid Amplification Test that can rapidly provide results as to whether the patient is GBS positive while in labor. If these tests are not available at the treating hospital, the choice to administer antibiotics during labor is based on the presence or absence of risk factors for infection. If the patient is either preterm, has a fever in labor, or has had her water ruptured for > 18 hours, antibiotic therapy during labor is recommended.

Antibiotic choices.

Although the preferred antibiotic choice for GBS treatment during labor is either Penicillin, Ampicillin or Cefazolin, there are several different types of antibiotic choices that can be used. The antibiotic selection will depend on the GBS culture results, maternal allergies, and individual patient medical needs. The goal of antibiotic therapy during labor is to achieve four hours of intravenous antibiotic treatment before delivery. Four hours of antibiotic therapy is generally considered adequate protection against serious infection for the newborn.

How does this affect my baby’s care after delivery?

Although only a patient’s pediatrician can decide if the infant needs additional testing for evidence of infection after delivery, the CDC has provided the following general guidelines as a framework of medical care for an infant born to a GBS positive mother. 

If I am GBS positive, how will this affect my future pregnancies?

Each pregnancy is treated separately as to whether a mother needs to be treated for GBS while in labor. A patient may be GBS positive this pregnancy but her next pregnancy be GBS negative. The only exception to this is that if a patient gives birth to a child that is treated for a severe GBS infection, all future pregnancies will require treatment for GBS.


Great strides have been made in reducing the incidence of GBS infection in newborns through the implementation of the guidelines recommended by the CDC. Since the 1990s, the number of cases of newborn GBS sepsis has declined by eighty percent. However, GBS remains the leading cause of serious newborn infections during the first week of life and continues to be a major focus of doctors and nurses in reducing neonatal infections. If you have additional questions as to the diagnosis or management of GBS infections either before or after your delivery, please feel free to discuss them further with your doctor.

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