What causes herpes to flare up?

There's no evidence that pregnancy causes herpes outbreaks, but approximately 75% of pregnant women with herpes will have an outbreak at some point during their pregnancy.
There's no evidence that pregnancy causes herpes outbreaks, but approximately 75% of pregnant women with herpes will have an outbreak at some point during their pregnancy.

Approximately 22% of pregnant women have genital herpes. While it's a manageable condition in most adults, herpes can be serious and even fatal for newborns. Fortunately, your risk of spreading it to your baby is very low, especially if you contracted it before your pregnancy. If you have it, your doctor will take measures to prevent you from passing it to your baby during delivery.

Usually your first herpes outbreak is the worst. Outbreaks generally become milder because your body makes antibodies to the virus. There's no evidence that pregnancy causes herpes outbreaks, but approximately 75% of pregnant women with herpes will have an outbreak at some point during their pregnancy.

Herpes can lie dormant for many years. Sometimes what appears to be a new case of herpes is actually a dormant case that is causing symptoms for the first time. If you don't know whether you have herpes, talk to your doctor about being tested.

After your initial herpes infection subsides, the virus travels to a bundle of nerves at the base of your spine. During this period it's latent, and you won't have any symptoms. Recurrent outbreaks happen when the virus travels from your nerves to the surface of your skin. Recurrent outbreaks may be triggered by:

The difference between genital herpes and oral herpes

Genital herpes can be caused by two different viruses, herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2). Oral herpes is usually caused by HSV-1. About 50% to 80% of adults have HSV-1. By age 50, about 90% of adults have been exposed to it. Oral herpes can be spread from the mouth to the genitals through oral sex, which is why some cases of genital herpes are caused by HSV-1.

Herpes in newborns

Both types of herpes viruses can cause neonatal herpes in newborns. It is most commonly spread to babies from their mothers during childbirth. However, babies can also get neonatal herpes from being kissed by someone with a cold sore. Rarely, herpes can be spread by touch, if someone touches a cold sore or genital sore and then touches a baby.

Neonatal herpes is a serious infection. It can cause:

  • Blindness
  • Inflammation of the membrane around your baby's brain
  • Seizures
  • Deafness
  • Sores on the skin, eyes, genitals, or mouth
  • Damage to your baby's organs, including the liver, lungs, and heart

Fortunately, neonatal herpes is also very rare, occurring in fewer than 0.1% of newborns born in the US each year. Most women with herpes give birth to healthy babies. The risk is greatest if you contract herpes late in pregnancy, since you won't have built-up antibodies to pass along to your baby. A new infection is also more likely to be active and present in the birth canal during delivery.

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How can you control your herpes while pregnant?

There are some steps you and your healthcare provider can take to minimize the risk to your baby even more. These include:

  • Make sure your midwife or obstetrician knows you have herpes.
  • If you have an active outbreak at the time of delivery, you may need to have a C-section.
  • Let your doctor know if you have any symptoms of an outbreak, such as tingling, itching, or pain, even if you don't have any sores.
  • If you have a vaginal delivery, your doctor may not break your water since it may help protect the baby in the birth canal.
  • A vacuum or forceps won't be used unless medically necessary since they can cause a break in your baby's skin that may allow the virus to get in.
  • A fetal scalp monitor won't be used unless medically necessary because it can break the baby's skin and allow the virus to enter.
  • Your doctor may prescribe antiviral medicine such as acyclovir to reduce your risk of having an outbreak during delivery or spreading herpes to your baby.
  • Since herpes can also be spread from cold sores, don't allow anyone with a cold sore to kiss your baby.

Once your baby is home, monitor them for about 3 weeks. If you notice any of the following symptoms, take your baby to the pediatrician and let them know you have herpes:

Preventing herpes during pregnancy

If you don't have herpes, it's important not to get it during pregnancy. If you test negative but your partner has genital or oral herpes, take the following precautions to avoid getting it:

  • Abstain from sex during outbreaks and use condoms at all other times.
  • Consider abstaining from sex completely during the last trimester.
  • Don't let your partner perform oral sex on you if they have oral herpes.
  • If you aren't sure if your partner has herpes, you may want to ask them to be tested.

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Medically Reviewed on 8/23/2021
References
American Sexual Health Association: "Herpes and Pregnancy."

Centers for Disease Control and Prevention: "Genital Herpes - CDC Fact Sheet." NHS: "Neonatal herpes (herpes in a baby)."

UT Southwestern Medical Center: "Genital herpes and pregnancy: Understanding the risks."

UpToDate: "Patient education: Genital herpes (Beyond the Basics)."