Cold Sores When Pregnant: Are They Dangerous?

Find out if your cold sore could cause complications for your baby.

pregnant belly, black and white photo
Photo: FOAP

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.

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.

What If My Partner Has a Cold Sore?

If your partner has a cold sore, he/she could transmit the herpes virus during oral sex. This is particularly worrisome in the third trimester, when a pregnant woman's immune system can't make antibodies that protect against herpes, according to the American Sexual Health Association (ASHA). By contrast, herpes acquired before pregnancy isn't usually cause for concern because active antibodies reach the baby through the placenta.

So why is contracting herpes during pregnancy a big deal? A mother with active genital herpes can pass the infection to her child during delivery. This neonatal herpes can come with a host of negative side effects ranging from birth defects to death.

To protect yourself (and your baby) from genital herpes during pregnancy, make sure you use protection (like a dental dam) during oral sex, especially if your partner hasn't been tested for STIs. Avoid oral sex with anyone who has a cold sore or feels one coming, since this could be a sign of herpes. It's also smart to avoid unprotected oral sex with a partner who has a history of cold sore; even if the sores aren't currently present, he/she might pass herpes onto you.

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