Group B Strep Test - Who & Why

Group B Strep Test, also called GBS is to screen a pregnant woman for the presence of group B streptococcus (GBS) in her vagina or rectum to determine the risk that she will pass the bacteria on to her newborn during labor and delivery, possibly resulting in a serious infection in her newborn called early-onset GBS.


Group B streptococcus — also called group B strep — is a common bacterium often carried in the intestines or lower genital tract. Although group B strep is usually harmless in adults, it can cause complications during pregnancy and serious illness in newborns.

When a woman is between 35 and 37 weeks of pregnancy or has preterm labor or preterm premature rupture of membranes, the health provider might recommend a GBS test.

Test Sample

A swab obtained from the vagina and rectum of a pregnant woman

A urine sample collected anytime during pregnancy may be used to detect significant numbers of GBS.

Test Preparation



A positive test for GBS in a healthy pregnant woman means that the bacteria are currently present in her vagina and/or rectum and she is at risk of passing the bacteria to her infant. She should be given antibiotics intravenously during labor to prevent spreading the bacteria to her baby. This treatment is known as intrapartum prophylaxis.

Pregnant women who have a urine culture positive for significant numbers of GBS any time during their pregnancy should receive appropriate intrapartum prophylaxis to prevent disease in their infants.

A negative result means that the woman is not likely to have GBS in the areas tested. No intrapartum prophylaxis is recommended unless she has other risk factors.



* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.