Page ContentGroup B Strep and PregnancyFirst Trimester | Second Trimester | Third Trimester | Postpartum Group B streptococcus is one of the many types of bacteria that live in the body and usually don't cause serious illness. It's found in the digestive and reproductive tracts of men and women, including the vagina and rectum. It's NOT a sexually transmitted infection. Pregnant women who are colonized (they have the bacteria present but no symptoms) can pass the bacteria to their baby during labor. This can cause infections in your baby's lungs and blood stream and may also cause meningitis. These infections, which can occur just after delivery or up to one week after delivery, can be severe and life threatening.Your doctor will test for Group B strep between 35 and37 weeks by swabbing the mother's vagina and rectum for a culture. If the result is positive, antibiotics will be given during labor to prevent infection being passed to the baby. The antibiotics work only if they are given during labor. If you had a previous baby with GBS infection or if your urine has GBS bacteria during this pregnancy, you are at higher risk of passing this to your baby during labor. You and your doctor will discuss your results and how this impacts your deliver.