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Cold sores in pregnancy

5-minute read

If you or your partner gets cold sores, you might be worried about what could happen when you're pregnant or have a new baby. Here's what you need to know about cold sores, and how to protect your baby from infection.

What are cold sores?

Cold sores are blisters that form on the lips, around the mouth and nose, or on the genitals. The blisters may form a crust after about 3 days. The sores go away by themselves within 2 weeks.

Cold sores are caused by the herpes simplex virus (HSV). They are easily spread to other people through touching, kissing or sexual contact. The sores are infectious until they have healed, however people who carry HSV but don't have cold sores can spread the virus through their saliva.

It is common for women who have had cold sores in the past to experience an outbreak while pregnant.

Types of herpes simplex virus

There are two main types of HSV:

  • HSV-1 causes mostly cold sores on the face and lips, and sometimes on the genitals
  • HSV-2 causes mostly genital herpes

Both viruses are transferred though contact of the skin, saliva or genitals, and the viruses stay in the body for life. The viruses do not always cause symptoms, so you can carry the virus without knowing it.

HSV-1 is very common, with about 8 in 10 Australians carrying it in their bloodstream. But only 1 in 3 people with the virus have ever had a cold sore. HSV-2 is less common.

Preventing herpes in your baby

Although the risk is small, babies can catch herpes. Herpes infections can cause serious problems in a baby, such as infections to the eyes and throat, brain damage and even death.

A newborn baby can catch HSV-1 and HSV-2 from being kissed or touched by someone with cold sores, or during childbirth — this can happen even if your genital herpes isn't active at the time of the birth.

Fortunately, most babies born to women who carry the virus are not affected.

But if you've ever had a cold sore or genital herpes and you become pregnant, it's important to tell your doctor or midwife about it. Together you can make a plan for managing herpes during pregnancy and birth.

Treating herpes while pregnant (or breastfeeding)

You can treat cold sores and genital herpes with:

  • aciclovir cream, available from a pharmacist without prescription
  • aciclovir or valaciclovir tablets, for which you need a prescription

These 'antiviral' drugs are known to be safe for pregnant and breastfeeding women and are known to be effective most of the time. The cost of these medications is not covered by the Pharmaceutical Benefits Scheme.

If you are pregnant and develop a cold sore, it's very unlikely to affect your baby. But as they're uncomfortable and infectious to others, it's worth treating.

What if I have genital herpes while pregnant?

You should take aciclovir or valaciclovir tablets, as above.

If it's your first outbreak of genital herpes, your baby may be more at risk because you haven't had time to develop immune protection against the virus, which also helps protect the baby.

Some women experiencing an outbreak of genital herpes might be advised to have a caesarean. This would prevent the herpes virus passing from mother to baby during a vaginal birth. But most women in Australia with genital herpes do give birth safely to healthy babies vaginally.

It's often recommended that women who have ever had genital herpes take antiviral tablets prior to the birth, even if the herpes isn't active at the time.

Talk to your doctor or midwife about the best course of action for your situation.

Protecting the newborn baby from herpes

It's important to maintain strict hygiene habits when caring for a new baby if you, or anyone in close contact with the baby, have cold sores.

If you have cold sores, you should:

  • cover cold sores when you're around the baby
  • avoid kissing your baby until the sores are completely healed
  • avoid touching the cold sores then touching your baby
  • wash your hands thoroughly before touching your baby

What if I have a cold sore while breastfeeding?

If you have cold sores, it is safe to breastfeed your baby as long as the cold sores are not on the breast or nipple.

If they are, it may be wise to breastfeed from the unaffected nipple only until the lesions have cleared up. You would express and dispose of breastmilk from the affected nipple. Breastmilk itself doesn't contain the herpes virus but it can be contaminated through the skin lesions.

Talk to your doctor or midwife as soon as you notice any cold sores on your breast or nipple.

If your baby gets herpes

It is very important that herpes in a newborn is recognised and treated by a doctor in hospital immediately. Signs of herpes in a newborn include:

  • blisters on the skin
  • fever
  • irritability
  • tiredness
  • lack of appetite

If you think your baby might have the herpes virus, don't wait to see if they get better — seek medical help. Tell medical staff if you or your partner carry the herpes virus.

Where to seek help

If you are worried about your baby, see a doctor or midwife, or take them to the hospital.

If you're not sure what to do or want more information, you call Pregnancy Birth Baby on 1800 882 436 to speak with a maternal child nurse.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: May 2019

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Call us and speak to a Maternal Child Health Nurse for personal advice and guidance.

Need further advice or guidance from our maternal child health nurses?

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The information is not a substitute for independent professional advice and should not be used as an alternative to professional health care. If you have a particular medical problem, please consult a healthcare professional.

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