Herpes Types I and II


The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.

What are herpes type I and herpes type II?

Herpes simplex virus type I (HSV-I) and type II (HSV-II) are very common viruses that cause a handful of conditions in women of childbearing age. The most common such conditions are cold sores (oral herpes) and genital sores (genital herpes). Usually, HSV-1 is the cause of oral herpes, while genital herpes is associated more with HSV-2, but there is overlap between the two viruses and the parts of the body on which they cause sores.

How common are herpes types I and II in pregnancy?

About 54 percent of people aged 14-49 in the United States have been infected with HSV-1 or HSV-2, although HSV-1 is much more common. Pregnancy is thought to increase the risk of either virus producing sores. This is due to hormonal changes and their effects on the immune system. 

How are herpes type I and herpes type II diagnosed?

Usually, the infection is recognized based on the patient noticing a sore and the diagnosis being made on the basis of the physical examination. The sore itself can be enough, but physical examination and your medical history may also reveal signs of infection such as fever, headache and swollen lymph nodes. A swab of fluid from the sore or a blood sample may be sent for laboratory analysis to identify the HSV-I or HSV-II virus.

Does herpes type I and herpes type II cause problems during pregnancy?

When caused by HSV-I the infection causing cold sores usually does not spread from the mouth. The main problem in such a case is mouth or gum pain, but the infection also may give you a fever or headache. A very rare complication of HSV-1 in the late second or early third trimester is a brain infection called herpetic encephalitis, which can be life-threatening.  Usually caused by HSV-II, genital herpes develops as one or more sores or blisters in the region of the vulva, vagina, or cervix. Along with pain and irritation or vaginal itching, you may suffer headache, body aches, fever, and vaginal discharge. Additionally, the HSV virus can become reactivated after your immune system has kept it in check for many years.

Do herpes type I and herpes type II during pregnancy cause problems for the baby?

In the case of cold sores due to HSV-1 limited to the mouth, pregnancy and delivery will be normal and the baby will not be at risk. In the case of genital sores, the virus may transfer to the baby, and in some cases cause a condition called neonatal herpes, meaning an HSV infection in babies who are up to 28 days old. Although rare, the condition can show up as an infection in the babys eye or throat, or in the brain, leading to behavioral or learning problems, or even death. It is possible that you can infect a newborn from a cold sore in your mouth also, but this is less common compared with infecting the infant from genital sores.

What to consider about taking medications when you are pregnant:

  • The risks to yourself and your baby if you do not treat the HSV-I or HSV-II
  • The risks and benefits of each medication you use when you are pregnant
  • The risks and benefits of each medication you use when you are breastfeeding

What should I know about using medication to treat herpes type I and herpes type II during pregnancy?

There are antiviral drugs that are offered. One is called acyclovir (Zovirax) and another is called valacyclovir. Both are effective against HSV-I and HSV-II. These same medications are used to treat infants for neonatal herpes, so there is no worry about the drug harming the baby. In fact, by taking one of these drugs, you are protecting your baby against possible herpes infection from you. To treat fever, you can use acetaminophen in the United States or paracetamol in many other countries, both of which are considered safe.

Who should NOT stop taking medication for herpes type I and herpes type II in pregnancy?

If you are given an antiviral drug to protect you or the baby from an HSV infection, you should not stop taking the treatment. If you need acetaminophen or paracetamol to combat fever during pregnancy, you should not stop taking the medication, since fever could be harmful to the baby.

What should I know about choosing a medication for herpes type I and herpes type II in pregnancy?

You may find Pregistrys expert reports about the individual medications to treat HSV-I and HSV-II here. Additional information can also be found in the sources listed at the end of this report.

What should I know about taking a medication for herpes type I or herpes type II when I am breastfeeding?

The antiviral medication acyclovir (Zovirax), is safe in mothers who breastfeed. Acetaminophen and paracetamol, given for fever, also are safe in mothers who breastfeed.

What alternative therapies exist besides medications to treat HSV-I and HSV-II during pregnancy?

There is no alternative to antiviral or anti-fever medication. However, there are preventive measures to help reduce the risk of spread in situations such as dental procedures. Dental treatment also can be postponed while you are getting your HSV infection under control.

What can I do for myself and my baby when I have herpes type I or herpes type II during pregnancy?

Follow the instructions of your physician, be assured that this is treatable, and make sure that your physicians and dentist are in contact (often this is done through electronic medical record systems).

Resources for herpes type I and herpes type II during pregnancy:

For more information about herpes type I and herpes type II during pregnancy, contact http://www.womenshealth.gov/ (800-994-9662 [TDD: 888-220-5446]) or read the following articles:


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General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.

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