Herpes and Pregnancy

Note: The Pregistry website includes expert reports on more than 2000 medications, 300 diseases, and 150 common exposures during pregnancy and lactation. For the topic Herpes Types I and II, go here. For the topic Genital Herpes, go here. These expert reports are free of charge and can be saved and shared.


Of the common diseases that patients might be diagnosed with, few seem to cause as many negative reactions as herpes. Yet, not only is it incredibly common—one figure has 90% of seniors testing positive for the virus—but it’s also a relatively benign, controllable illness in the great majority of people.

That said, there is a big BUT here. Herpes can be harmful to a newborn baby, causing organ damage or even death. For this reason, pregnant women who might have herpes are followed very closely, with multiple precautions in place to protect our new arrivals. Let’s discuss what herpes is, what it does, and what providers do to keep babies healthy.

Names and Numbers

“Herpes,” as the term is used, is actually short for herpes simplex; the virus itself is known as the herpes simplex virus (HSV). HSV is part of a family of viruses, and has some well-known cousins—for example, the chicken pox virus.

There are technically two viruses which cause herpes (the term we’ll use in this blog to mean herpes simplex). HSV-1 has historically been said to cause “oral herpes” and HSV-2, “genital herpes.” However, although they are technically two different strains of virus, either one can show up in either location, and this has increasingly been the case.

Herpes for Most of Us

Herpes is not that difficult to transmit. Infected individuals can transmit the virus from saliva, or from infected areas on the skin. This is how children generally become infected, often with oral herpes. Genital herpes, on the other hand, is mainly sexually transmitted.

Once infected, most individuals have no symptoms. The next most common scenario is small bumps on the skin which may rupture, leaving painful ulcers, and/or get crusty. There may be ulcers in the mouth or inside the vagina, both of which can be quite painful.

The bumps and ulcers, if present, generally heal in a few weeks. The virus, however, doesn’t go away; it goes into hiding in the body’s nerves. As bad as this sounds, there are usually no symptoms with this; however, the virus can reestablish itself, especially during times of stress, and cause rashes and ulcers in the future. Fortunately, most recurrences don’t last as long as the first infection.

Rarely, herpes can cause more serious illness in otherwise healthy people. The two most common serious complications seen are eye infection and brain infection (encephalitis). For most of us, that’s about it as far as risk from herpes goes. But for individuals with poorly functioning immune systems, the risks are greater. And one group in the lower-immunity category concerns us today: newborns.

Herpes and Pregnancy

During pregnancy, if Mom’s membranes are intact, herpes doesn’t cause problems for the fetus. The problem comes when a baby picks up the virus during Mom’s labor and delivery. It can affect the liver, lungs, blood and brain, causing severe, life-threatening disease.

For this reason, the pregnancies of women who might ever have had herpes are followed very carefully. Suspicious-looking rashes or ulcers can be tested. Historically, the most common test was the viral culture (basically growing the virus). There is now newer DNA technology: the polymerase chain reaction (PCR) more readily detects the germ. Many providers would test any lesions (rashes or ulcers) and, if positive, start medication. (Herpes is one exception to the rule: Many viruses don’t have a medicine that can take them away. While herpes can’t be cured, lesions can be eradicated with antiviral medicine.) Women with lesions would also often have their baby delivered by C-section.

More recently, we’ve come to realize that herpes can be transmitted by infected people who have no symptoms. This especially happens during an initial infection but can also happen during subsequent infections. For this reason, there has been a tendency to treat all women with a history of herpes beginning the 36th week of pregnancy. The goal here is to prevent the transmission of the virus during labor and delivery.

Despite this strategy, some newborns get herpes. If there is a chance of this (for example, if the mother had a vaginal herpes ulcer during delivery), infants will get multiple tests (the areas include skin and blood). Any positive test means that the baby receives treatment for anywhere between 10 and 21 days. Even with no history of herpes, many sick infants up to six weeks of age—those who develop a fever, for example—are tested and treated for the virus.

Lessons for Mom-to-Be

Because herpes is so common, it’s tough to avoid. If you’re convinced you have not had the infection, but have a partner who does, you could consider abstaining from sex until all areas have healed, and, for extra protection, having your male partner use a condom even if he doesn’t have herpes ulcers.

Most importantly, if you have had herpes, let your obstetric provider know. Also let her know if you have any unusual ulcers or bumps, especially in your vaginal area. Do, however, realize that many cases have no symptoms. Also, babies can get herpes from lesions on other parts of the body or from the mouth of an infected person.

Additionally, be on board with any treatments that might be recommended or needed for you or your newborn suspected of having herpes. This is another situation where an unexpected hospital stay for your baby might be necessary to ensure good health.

Finally, take comfort in the fact herpes should not constitute a stigma. A very large percentage of people will get the virus, and with good medical care and monitoring, it shouldn’t cause a problem in the great majority of people—including the newborns of infected mothers.

Stan Sack
Dr. Stan Sack has 29 years’ experience as a primary care pediatrician in Massachusetts and Florida. A medical writer since 2015, he enjoys blogging on topics that are on parents’ minds but are covered less often in books and on websites. He lives in the Florida Keys with his family and enjoys healthy cooking, fitness activities and singing in his spare time.

Leave a Reply