lizzie,
What is group B streptococcus?
Group B strep (GBS) is a kind of bacteria that many people harbor in their intestinal tract. The bacteria may also inhabit (or "colonize") your vagina as well, where it can be passed on to your baby during labor and birth.
Approximately 10 to 30 percent of pregnant women carry GBS in the vagina or rectum or surrounding area. While GBS is generally harmless in healthy adults, it may cause stillbirth and serious infections in babies.
Although sexual transmission is possible, Group B strep is not considered a sexually transmitted infection since your genital area may become colonized from bacteria you carry in your own gastrointestinal tract. It's also not the same as group A strep, the bacteria that usually cause strep throat.
Why do I need to be tested for group B strep?
Getting screened for GBS late in pregnancy – and receiving treatment with antibiotics during labor if you're a carrier – will greatly reduce your baby's risk of becoming infected.
For this reason, the Centers for Disease Control and Prevention (CDC), the American Academy of Pediatrics (AAP), and the American College of Obstetricians and Gynecologists (ACOG) recommend that all pregnant women – with two exceptions – be routinely screened for GBS at 35 to 37 weeks.
The two exceptions: women who have previously had a baby with a GBS disease and those who have had a urinary tract infection caused by GBS during their current pregnancy. These women don't need to be screened because they're already considered at high risk and will automatically be treated during labor.
Before pregnant women were routinely screened and treated, approximately 2 to 3 babies per 1,000 live births suffered from what's known as early-onset GBS disease, a life-threatening illness that shows up in the first week of life (most often in the first 24 hours after birth). Now, there are about 0.35 cases per 1,000 live births.