I was due three days ago and also have a cold sore. This is a fairly common occurance for me. I use compeed cold sore patches on mine. It seals the sore to avoid contaminating anyone else. And also heals so much faster. I put the patch on clean dry lips. Then use my lip liner and a slick of lipstick as normal. My friends, family and colleagues often can't even tell I have a sore despite my lip being swollen-it usually feels much bigger than it looks due to the throbbing pain. I wouldn't worry too much I contracted the virus myself because my mum couldn't stop kissing me as a little one.
Tell your doctor! They can give you valtrex or acyclovir and get you cleared up really quick! I took acyclovir my whole pregnancy to prevent break outs - totally safe according to my doctor. The sooner you get treated the sooner you can kiss that gorgeous baby!
Working in the dental field, we would tell patients to use sun screen and peroxide on the lips to prevent outbreaks. Usually we don't advise kissing your baby because the virus is still present in your saliva without an outbreak. In some infants, the outcome has been deadly. Obviously, I am not a medical doctor so you may want to speak with your physician about risks.
"In young babies, in particular, the herpes virus can spread to the brain and other organs, causing serious, potentially permanent or fatal damage."