A: Group B Streptococcus is a common bacteria of the vagina and lower intestines, found in 10 to 35% of healthy women. It's different than Group A Strep, the cause of strep throat. While GBS doesn't cause symptoms in most women, it can cause a major infection in newborns.

Thousands of newborns become infected with GBS each year, usually from exposure during labor and delivery. Once your bag of water breaks, either before or during labor, GBS has the opportunity to migrate into the uterine cavity, putting you and your baby at risk of infection. Infections are more common after a lengthy labor, or after the bag of water has been ruptured for many hours. Intravenous antibiotics given during labor to women who carry GBS will substantially lower the chance of developing a serious newborn or maternal infection.

There are different medical approaches to treating GBS. Many obstetricians test all pregnant women for GBS near the end of pregnancy and provide intravenous antibiotics during labor to anyone who has had a positive test.

Other obstetricians provide antibiotics to women who have a higher chance of developing an infection, such as women who labor more than 12 hours after the water bag breaks, or to those women who already show signs of an infection, such as a fever.

Once you test positive for GBS, we assume that you will carry this bacteria off and on during your lifetime. Treatment with antibiotics only provides temporary suppression of the bacteria. Rather than checking for GBS during each pregnancy, most doctors will treat you as GBS positive if you have ever had GBS on a screening test, or if you ever had a GBS infection. Antibiotics would then be provided during labor to prevent the possibility of a serious infection.