1 in 3 women have group strep B. It is a common thing to have. It becomes active and inactive at various times in your body. It is only really a problem if it is active in your vagina when you give birth. The risk is after the waters have broken before the baby comes out.
The test for it is done during pregnancy, but is very unreliable. If you get a positive result at 37 weeks, it could be gone by the time you get to 40 weeks. But likewise, if you have a test earlier and it is negative you cannot for certain say that you are not at risk for it.
As MrsZuko says it is a symptom-less infection.
The antiboitics that can be given during labour REDUCE the risk of passing on the infection to the baby they do not eliminate it.
When a baby gets a group strep B infection it can be leathal.
About 1 in 1000 babies contract group strep B, and of those 1 in a 1000, 1 in a 1000 might die. Many may have other problems due to the infection.
It is important to realise how serious this condition is, but also realise how uncommon it is. It is vital that all mums watch for signs of infection in the baby in the first 48 hours after birth, and get hospital help as soon as possible if at all worried.
The debate about antibiotics during labour and whether to test for group strep b during pregnancy are contraversial ones. There are loads of links to various websites if you search the group strep b theads on mn.