While most women with genital herpes have healthy babies, a small number pass the virus on to their babies during labor and delivery. For this reason, it is especially important for pregnant women to recognize the symptoms of genital herpes and to seek immediate medical treatment if they think they could be infected. Pregnant women should tell their health care provider if they have had herpes in the past, so the provider can take any necessary steps to protect their babies from the infection.
What causes genital herpes?
Herpes is caused by herpes simplex viruses (HSVs), which are similar to the viruses that cause chickenpox and shingles. After the initial infection, HSVs can hide within nerve cells, where the body’s immune system cannot reach them. Then, under the right conditions, the viruses can launch new attacks.
There are two main kinds of HSVs:
- HSV-1, which usually causes cold sores around the mouth and lips
- HSV-2, which usually causes genital sores.
However, either type can infect oral or genital areas, and pregnant women with genital sores caused by either form of HSV can pass the infection on to their babies.
Environmental influences—such as heat, friction, sexual intercourse, menstruation, fever or emotional stress—may trigger a new outbreak of sores. The average infected person experiences four or five recurrences a year. The outbreaks tend to become less frequent and less severe with time.
- Sexual intercourse
- Oral-to-genital contact with an infected person
An infected person can spread the virus from one part of the body to another with unwashed hands. For example, persons who have cold sores always should wash their hands thoroughly after any contact with saliva before touching the genital area.
Children often become infected with HSV-1 during the first years of life. This may occur when a child has direct contact with:
- Herpes sores (for example, being kissed by a person with a cold sore)
- Virus-containing saliva (for example, touching their lips with their fingers after contact with infected saliva)
What are the symptoms of genital herpes?
Shortly after a person contracts herpes, clusters of small blisters may appear in the genital area. These blisters itch and become painful. Then they break, leaving painful ulcers. Fever, fatigue, aches and pains, and a urethral or vaginal discharge often occur.
Health care providers diagnose herpes by:
- Examining the sores
- Doing a swab of the blisters, then ordering lab tests
The lab tests may be a culture or, sometimes, a newer test called polymerase chain reaction (PCR). The provider also may do a blood test to help confirm the diagnosis.
The first, or primary, attack may last as long as 2 to 4 weeks. Recurrent outbreaks generally are shorter and milder.
Most herpes infections, both primary and recurrent, do not produce any symptoms. These symptomless (sometimes called silent) infections generally go undiagnosed. As a result, about 90 percent of people who are infected with genital herpes do not know they have it (3). However, individuals with symptomless infections can pass the virus on to others, including a newborn baby.
A provider may recommend one of these drugs when an individual has a primary or recurrent attack of herpes with severe symptoms. The provider also may recommend daily treatment with one of these drugs to help reduce the number of attacks in individuals who have them often.
Pregnant women who have a primary attack of herpes often are treated with acyclovir (3, 4). This drug appears safe in pregnancy and has not been associated with birth defects with more than 20 years of use (3, 5). Valacyclovir and famciclovir usually are not recommended in pregnancy because less is known about their safety (3).
What risks does herpes pose during pregnancy?
About 1 in 4 pregnant women is infected with genital herpes, although most do not know it (3). Fortunately, only a small number pass the infection on to their babies.
Women who acquire genital herpes for the first time near the time of delivery have a 30 to 50 percent chance of passing the infection on to their babies during a vaginal delivery, whether or not they have symptoms (4). The risk is so high because a newly infected pregnant woman has not yet produced disease-fighting antibodies that could help protect her baby during delivery. Studies suggest that about 2 percent of pregnant women acquire herpes for the first time during pregnancy (3).
Women who have had herpes before pregnancy and have a flare-up or silent infection at the time of vaginal delivery have only about a 3 percent chance of infecting their babies (3). Sometimes, what appears to be a first, severe episode of herpes during pregnancy actually can be a flare-up of an old silent infection. These women have a low risk of infecting their babies. Blood tests sometimes can help determine whether a woman has a new infection or a recurrence of an old one.
Are there other ways in which a baby can become infected?
While most babies get herpes from their mothers at delivery, on rare occasions, a baby can become infected before birth (3). A small number of babies acquire herpes after birth (for example, if someone with a cold sore kisses them). A person with a cold sore should not kiss a baby or touch a baby after touching the cold sore.
What are the symptoms of herpes infection in the newborn?
Some infected newborns develop skin or mouth sores or eye infections. When the infection remains limited to these organs, most infected babies develop normally, although serious permanent damage to nerves or the eyes can occur.
However, herpes infections in newborns often spread to the brain and many internal organs. Infected babies may appear irritable, eat poorly and have seizures. Even with treatment, about 30 percent of infants with widespread infections involving the internal organs die, as do about 4 percent of those with brain infections (3). Many babies who survive widespread infections and brain infections develop lasting disabilities, such as intellectual disabilities, cerebral palsy, seizures, and vision or hearing loss.
How are infected newborns treated?
Infected newborns are treated with acyclovir (4, 6). This drug is quite successful in treating localized infections of the eyes, skin or mouth. It is important to treat infected babies early, before the infection spreads, because acyclovir is less effective once the infection has spread to the brain and other internal organs.
How can the baby be protected from infection if the mother has herpes?
If a pregnant woman has a history of genital herpes, her health care provider examines her carefully for any signs of infection when she goes into labor. When a woman has an active infection (primary or recurrent) at the time of delivery, her baby usually can be protected from infection by a cesarean delivery (3, 5). A vaginal delivery is safe for most women with recurrent herpes as long as they don’t have signs of infection at delivery.
Some providers recommend that women with a primary infection during pregnancy or with recurrent flare-ups take acyclovir for the last month of pregnancy. Some studies suggest that this treatment may help prevent active infections during labor and delivery and help reduce the need for cesarean delivery (3, 5).
However, most mothers of infants with newborn herpes infections have no signs or symptoms of active herpes infection at delivery (3). Providers have not yet developed a good way to protect babies when their mothers have silent infections at delivery. Virus-culture tests are not helpful during labor and delivery because results are not available for 1 to 3 days. Researchers are seeking to develop vaccines, as well as blood tests that may offer rapid diagnosis during labor, in order to prevent more newborn infections.
How can a woman avoid getting genital herpes during pregnancy?
A pregnant woman who does not have a history of genital herpes should take special precautions to stay infection-free, especially in the last trimester, when risk to the baby is highest. If her partner has a history of herpes, she may want to ask her health care provider about taking a blood test to find out whether or not she is infected (she could have had a silent infection). If she does not have herpes, her provider may recommend that she avoid intercourse and oral-genital contact in the last trimester. Before the last trimester, she and her partner should avoid intercourse when he has symptoms of infection, and he should wear a condom when he does not have symptoms (because he cannot tell if he has a silent infection). He also can ask his provider about taking preventive antiviral treatment, which can reduce the risk of passing on the infection to his partner.
Does the March of Dimes fund research on newborn herpes infections?
The March of Dimes has supported a number of grants aimed at preventing and treating newborn herpes infections. For example, one recent grantee is seeking to develop a vaccine for newborns that can boost their immune response and help prevent brain damage and deaths resulting from newborn herpes infection. Another is investigating how the virus invades the newborn’s central nervous system in order to develop antiviral drugs that can prevent complications of newborn herpes infections.
- Centers for Disease Control and Prevention (CDC). Genital Herpes Fact Sheet. Updated 1/4/08.
- Gardella, C., and Brown, Z.A. Serologic Testing for Herpes Simplex Virus. Contemporary Ob/Gyn, October 2007, pages 54-58.
- American College of Obstetricians and Gynecologists (ACOG). Management of Herpes in Pregnancy. ACOG Practice Bulletin, number 82, June 2007.
- Centers for Disease Control and Prevention (CDC). Sexually Transmitted Diseases Treatment Guidelines 2006. Morbidity and Mortality Weekly Report, volume 55, RR-11, August 4, 2006.
- Brown, Z.A., et al. Genital Herpes Complicating Pregnancy. Obstetrics and Gynecology, volume 106, number 4, October 2005, pages 845-856.
- Kimberlin, D.W., et al. Natural History of Neonatal Herpes Simplex Virus Infections in the Acyclovir Era. Pediatrics, volume 108, number 2, August 2001.