At about 36 weeks in your pregnancy, you will be tested for Group B Streptococcus (GBS). For this test, a swab is used to take cell samples from your vagina and anal area. Many women are carriers of this bacteria, and it causes no problems for them, but GBS can be passed to a baby during birth and cause illness in the newborn. If a woman tests positive for GBS, she will be given antibiotics during labor to help prevent the baby from being infected. For more detailed information go to Group B Streptococcus and Pregnancy from ACOG.