According to what I know (I'm not sure), it's transmitted by eg. 黏膜分泌,口水之類, not by blood, so even you really has this disease, you will not transmit it to your baby.
If it's type I 疱疹一型, (should be your case, it happens on mouth corner or face as doctor told you that you should have it before), the virus will not be in 陰道.
People can have nature birth, no problem at all.
But if during pregnancy, you have 病發, you have to see the doctor, but still not problems.
For those mothers if they have type II疱疹二型, the virus maybe in the 陰道, they can not use nautral birth (maybe when 病發), they must 開刀, becuase if the baby pass 陰道, it may infect the virus, it will die or get very serious problem.
I read a magazine and also some websites states, 70% of people infected 疱疹 (I think type I) before, but 90% of people do not 病發 and so many people don't know.
Most people infected this when they were young, because children are easilier to be infected than audlts.