I'm wondering what you mean by a GBS pos baby--do you mean a sick baby, or a baby who has shown some sign through testing, of carrying, or possibly carrying, GBS?
Probably best to treat a baby who is actually already sick, with antibiotics. GBS sepsis is just so fast-acting and hard on neonates. On the other hand--if the baby is NOT sick, but there is some reason (from labs) to suspect baby is a carrier--then yes, a person could do other things to minimize possibility of baby getting sick.
Can you clarify this at all?