Cold sore in early pregnancy, is it harmful?

Hi all, i'm 8 weeks 4 days and just found out that i have cold sore on my upper lips (the medical terms is herpes labialis). This is not the first time, since it already went on and off for the last 4 years, and usually come back when my imune system is low.. I've already prescribed with zovirax cream. Is there anyone out there with the same condition? Is it harmful for your baby?