Is A Cold Sore Dangerous During Pregnancy?

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Cold Sore Pregnancy

The short answer is probably not, but that is not the whole story, so keep reading. Cold sores – also called fever blisters – are not caused by a cold virus. They are caused by the herpes simplex virus (HSV). There are two types. Type 1 (HSV-1) causes cold sores. Type 2 (HSV-2) causes genital herpes. Cold sores are very common and not normally dangerous during pregnancy, but in some rare cases, they can be. 

Cold Sore Basics

A cold sore is a small, painful blister, or group of blisters, that forms on your lip or mouth area. HSV-1 spreads easily from person to person because the virus lives in saliva and in the fluid that fills the blister. The virus spreads most easily when the blisters rupture and drain. This infection is so common that almost 70 percent of people get the virus, usually before age 5.

HSV-1 is not a serious infection for children or adults. The cold sores usually clear up on their own within three weeks. However, once you have been infected, the virus stays in your body and can reactivate and cause a new outbreak, usually when you are under stress. Cold sores don’t usually need to be treated. An antiviral medication can shorten the infection but not cure your body of the virus.

  • If you have a cold sore during pregnancy, wash your hands frequently. Avoid touching your cold sore and then touching any other area of your body, especially your genital area.
  • Do not let anyone with an active cold sore kiss your baby. If you have the cold sore, wash your hands before touching your baby until the cold sore scabs over.

It is important to know that neonatal herpes is rare, even when a mother has an active infection late in pregnancy. Only about 10 out of 10,000 babies become infected.

Neonatal Herpes

Although HSV is not a major problem for children or adults, it can be a major problem for a newborn infant. In fact, untreated neonatal herpes can be deadly. A newborn’s immune system may not be strong enough to fight off the virus.  It may spread to the brain, liver, lungs, and kidneys.

Neonatal herpes is almost always caused by HSV-2 infection, not by cold sores. A newborn can be infected when he or she passes through the mother’s birth canal. HSV-2 is a sexually transmitted disease. About 10 to 14 percent of people become infected with genital herpes. Blisters can form in the genital or anal area. Like HSV-1, once you have the infection, it is with you for life and can reactivate.

Although HSV-1 rarely causes neonatal herpes, because it stays near your mouth, there are some rare occasions in which HSV-1 can be dangerous for a newborn. HSV-1 is most contagious when the infection is active–blisters around the mouth are open and draining. Once they crust over the chance of spreading the infection is less. Here are two ways cold sores might be dangerous for your baby:

  • If you or someone else has an active HSV-1 infection, the infection could spread to a newborn through kissing during the first 6 weeks of life. If someone with an active infection touches a cold sore and then handles a baby, this is another possible way to spread the infection.
  • If you have an active cold sore and touch your mouth and then touch your genital area, you could cause an HSV-1 genital infection. Your baby could then catch the infection during birth if you have a vaginal delivery.

Symptoms of HSV Infections

The first warning of HSV may be a tingling, burning, or itching in the area where blisters will form. For HSV-1, you may have a sore throat or tender neck glands. You may feel a bit tired, have slight nausea, or have a headache. An old infection might be triggered by a cold, stress, fatigue, or a sunburn.

Symptoms of HSV in a newborn usually start within 2 to 12 days but could occur anytime in the first 6 weeks. They can include:

  • Fever
  • Poor feeding
  • Skin blisters

Untreated HSV that spreads through a baby’s body can cause difficulty breathing or seizures. It is important to know that neonatal herpes is rare, even when a mother has an active infection late in pregnancy. Only about 10 out of 10,000 babies become infected.

If a baby is diagnosed with neonatal herpes, the treatment is an antiviral drug given intravenously in the hospital. This will usually prevent the infection from spreading and becoming serious. If a mother is diagnosed with an active genital infection late in pregnancy, a C-section may be advised. This will prevent the baby from being exposed to the infection in the birth canal.

Key Takeaways

  • Cold sores are common, and they are unlikely to affect your pregnancy or your baby. 
  • If you have a history of genital herpes, let your doctor know. This is especially important if you have any genital outbreak late in pregnancy.
  • If you have a cold sore during pregnancy, wash your hands frequently. Avoid touching your cold sore and then touching any other area of your body, especially your genital area.
  • Do not let anyone with an active cold sore kiss your baby. If you have the cold sore, wash your hands before touching your baby until the cold sore scabs over.
  • Adults do not usually need treatment for cold sores, but if you have a cold sore that is very uncomfortable or lasts more than 2 weeks, ask your doctor if you can use an antiviral cream or oral antiviral medication.
Christopher Iliades
Dr. Chris Iliades is a medical doctor with 20 years of experience in clinical medicine and clinical research. Chris has been a full time medical writer and journalist since 2004. His byline appears in over 1,000 articles online including EverydayHealth, The Clinical Advisor, and Healthgrades. He has also written for print media including Cruising World Magazine, MD News, and The Johns Hopkins Children's Center Magazine. Chris lives with his wife and close to his three children and four grandchildren in the Boston area.

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