Group B Streptococcal Screening

Group B streptococcal (GBS) screening is a medical test used to detect the presence of Group B streptococcus bacteria in pregnant women. The test is typically performed between 35 and 37 weeks of gestation.

Purpose of the Test

The purpose of GBS screening is to identify pregnant women who are colonized with GBS, which can be transmitted to the baby during delivery. This is important because GBS can cause serious infections in newborns, including sepsis, pneumonia, and meningitis.

How the Test is Performed

The GBS screening test involves collecting a sample of cells from the vagina and rectum using a swab. The sample is then sent to a laboratory for analysis. The test can detect the presence of GBS bacteria in the sample.

Types of Tests Used

There are two types of tests used for GBS screening:

• Culture test: This is the most common type of test used. It involves growing the bacteria from the sample in a laboratory to detect its presence.
• Polymerase chain reaction (PCR) test: This is a more rapid test that uses DNA analysis to detect the presence of GBS bacteria.

Interpretation of Results

The results of the GBS screening test can be:

• Negative: This means that no GBS bacteria were detected in the sample.
• Positive: This means that GBS bacteria were detected in the sample. In this case, the woman will typically receive antibiotics during labor to reduce the risk of transmission to the baby.

Risk Factors for GBS Colonization

Certain factors can increase a woman's risk of being colonized with GBS, including:

• Prior history of GBS colonization or infection
• History of a previous baby with GBS disease
• African American ethnicity
• Younger age (less than 20 years old)

Prevention and Treatment

For women who test positive for GBS, antibiotics are typically administered during labor to reduce the risk of transmission to the baby. The most commonly used antibiotic is penicillin.

Recommendations

The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women be screened for GBS between 35 and 37 weeks of gestation. Women who test positive should receive antibiotics during labor, unless they have a history of severe penicillin allergy.