Normally there are a lot of lactobacilli or "good" bacteria present in the vagina, and these bacteria keep other bacteria and yeast
from causing symptoms of infection
. It is important to keep the "good" bacteria healthy so that they can fight the "bad" ones like the ones that cause BV (gardnarella, etc). You can do this by taking
probiotics and also live culture yogurt.
BV is not really a sexually transmitted disease, and won't harm a developing baby.