Group B streptococcus (GBS) are common bacteria which are often found in the vagina, rectum or urinary bladder of women. This is not the same bacterium which causes strep throat. Infections from GBS are usually not serious for a woman and are readily treated with antibiotics. However, when a woman becomes pregnant, the whole outlook changes.There is no sure way to prevent the GBS bacteria from being passed to a newborn at the time of birth and although it is very rare, and despite medical treatment, some babies still die as a result of complications from a GBS infection. Your doctor would like to help prevent this from happening. GBS usually does not cause infections in pregnant women, the concern is for the baby.