Cold sore is the nice way to say herpes virus.
I am positive to both herpes simplex type 1 (most common to face/mouth) & type 2 (STI passed on to the genital region).
Only if you have an active type 2 sore whilst having a natural birth can be dangerous to your baby.
My son was kept in special care nursery for first 10days of his life to be treated as a precaution as if your baby contracts it to his cranium during birth it can be very dangerous, even fatal.
I'm happy to say my son's test results all came back negative and am extremely grateful the staff in the hospital still treated my son as 'worst case scenario' while waiting for tests results to ensure IF he had contracted the virus it was managed from the first few moments of his life.
My son does have antibodies for type 1 Herpes, and my Mother old me this is a good thing and she has been doing microbiology/pathology for more than 20years!