Women’s Health Care Resources

Obstetrics Services

Group B Strep in Pregnancy

Group B Streptococcus (GBS) is a type of bacteria that can be found in up to 40% of pregnant women. If a woman is positive for GBS, she can pass it on to her baby during delivery. Some babies who get GBS do not have any problems but this can cause major health risks and even death.

GBS is a bacteria that can be found in the digestive, urinary and reproductive tract. In women, it is commonly found in the vagina and rectum. Being colonized with GBS does not pose any danger and if a woman is not pregnant, she does not need to be treated. However, if a woman is pregnant, she can pass GBS to her baby. Between 1-2 of every 100 babies whose mothers have GBS become infected. If a baby develops GBS infection, this can lead to inflammation of the baby’s lungs, brain and spinal cord. GBS infection can lead to death of the newborn in about 5% of cases. Because of the risk of these outcomes, a woman who is positive for GBS is treated with antibiotics during labor.


Testing for GBS is most accurately done with cultures. With cultures, a sample is taken from the vagina, perineum and rectum during pregnancy. Cultures are typically done between at 36 weeks gestation.

The test results are typically valid for 4 weeks. If you test positive, you will be treated with antibiotics during labor to reduce the risk of infecting your baby.


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