Cold sores are a strain of herpes, meaning they are extremely contagious and can recur, says Susan Grant, M.D., an OB-GYN in New York City. They can appear at any time, especially when your body is under stress or going through hormone fluctuations, making pregnancy a prime time for outbreaks.
RELATED: 17 Tips for a Healthy Pregnancy
You may feel (but not see) a bump or notice a tingling on your lip, indicating that an outbreak is about to occur. But because it is a localized infection, there is nothing to worry about and no way for the herpes virus to pass through the protective placenta to your growing fetus, Grant says.
However, if you do have an outbreak after giving birth, do not kiss your baby, and don't touch the sore without immediately washing your hands afterward with antibacterial soap, Grant warns. You're most contagious during the weeping stage, when the blister opens and reveals a reddish area.
You can reduce the duration of an outbreak with an over-the-counter cold sore remedy such as docosanol (Abreva) and prescription anti-viral medications, such as acyclovir (Zovirax), both of which are considered pregnancy-safe.