URINE CULTURE: Ideally your provider should do a urine culturefor GBS and other bacteria (this is not the standard prenatal urine “dipstick” check) at your first prenatal visit. Having GBS in your urine is a risk factor associated with early-onset GBS disease. If your urine tests positive, your provider should consider you as “GBS colonized” for this pregnancy so that you receive IV antibiotics for GBS when labor starts or your water breaks.
SWAB TEST: It is now the standard of care in the US for all pregnant women to be routinely tested for GBS during their 36th or 37th week during each pregnancy unless their urine already cultured positive in the current pregnancy or they have had a previous baby with GBS disease. (Since levels of GBS can change, each pregnancy can be different.) Your provider will perform a swab test of both your vagina and rectum and receive the test results in 2–3 days.
Inform your provider if you are using antibiotics and/or vaginal medications which may cause false negative results.(1)
It’s important to know that:
A woman may test negative if her GBS colonization level at the time of the test was below the level of detection.
A woman’s GBS status can change so a woman could test negative but be colonized later in pregnancy.
Test results are only considered to accurately (95%-98%) predict a woman’s colonization status at delivery if she delivers within 5 weeks of her test. A woman may need to be retested if she has not yet given birth within 5 weeks of being tested.
RAPID NAAT TESTING: Some hospitals will offer rapid DNA-based tests which can be performed during labor or any time during pregnancy with results in just a few hours. These tests can help supplement your routine GBS testing because:
Your GBS status can change by the time you go into labor.