You're a group b strep carrier. If it would get passed on to your baby during childbirth, it could cause a serious infection in the blood (sepsis) and brain (meningitis). It's definitely life-threatening to a newborn, that's why they'll give you iv antibiotics during labor.
Don't worry, it's not a sexually transmitted disease or spread in any other matter except during childbirth. I've read that about 1 in 4 women have this condition. As long as you get the antibiotics you and your baby should be fine!