What do cold sores during pregnancy mean?

According to MedlinePlus, cold sores during pregnancy indicate the presence of the herpes virus in the mother. While congenital herpes, in which herpes is passed on to the baby in the uterus, is rare, it is possible to pass the herpes virus on to a newborn.

Fit Pregnancy explains that the herpes virus is extremely contagious. As a result, a mother with a cold sore should not kiss her baby. She should also wash her hands with antibacterial soap every time she touches the sore. A cold sore is at its most contagious when the blister opens, becomes red and reaches its "weeping" stage.