Prenatal Testing Basics: Group B Strep Test
Who has it, when, why, and what the results mean.
When is the test taken?
The Group B strep test, which screens for potentially dangerous Group B streptococcus (GBS) infection, is usually given during weeks 35 to 37.
Who needs to take the test, and why?
Many healthcare providers routinely test all pregnant women for Group B streptococcus, a bacterium that lives in the reproductive and genito-urinary systems. Group B strep (which is different from Group A streptococcus, the kind that gives you strep throat) can be present in anyone, but few people become sick from it. It is a concern during pregnancy, however, because it can cause urinary tract and uterine infections, and, if it is transmitted from mother to baby during birth, it can be very harmful to the baby. If your doctor doesn't offer the test, you may want to ask for it: The Centers for Disease Control and Prevention currently advise all healthcare providers to give the test to any patient who requests it.
Some practitioners prefer to bypass testing in favor of treatment for all women who have one or more of the following risk factors: preterm labor, a prior child with GBS infection, fever during labor, presence of GBS in urine, or rupture of membranes ("water breaking") before 37 weeks or more than 18 hours before delivery.
In this quick and painless test, your practitioner takes a swab of your vagina and rectum. The sample is sent to a lab for a culture to test for the presence of Group B strep.
When are test results available, and how are they interpreted?
Results available within 24 to 48 hours. If your test shows that you carry the bacterium, you'll be treated with intravenous antibiotics during labor and delivery. Rest assured that, although about a third of pregnant women carry the GBS bacterium, few of their babies actually develop an infection--perhaps 1 out of every 200.
If a baby does become infected with GBS, symptoms can vary. Babies with an "early-onset" infection--which develops within 7 days of birth -- may suffer from pneumonia, sepsis (blood infection), and/or meningitis. Babies with "late-onset" infection -- which develops between 7 days and 3 months of age -- are most likely to have meningitis. Infected babies are treated with intravenous antibiotics for about 10 days. In most cases, this treatment is effective in preventing lasting harm to the baby.
All content here, including advice from doctors and other health professionals, should be considered as opinion only. Always seek the direct advice of your own doctor in connection with any questions or issues you may have regarding your own health or the health of others.