If a woman with genital herpes has virus present in the birth canal during delivery, herpes simplex virus (HSV) can be spread to an infant, causing neonatal herpes, a serious and sometimes fatal condition. Neonatal herpes can cause an overwhelming infection resulting in lasting damage to the central nervous system, mental retardation, or death. Medication, if given early, may help prevent or reduce lasting damage, but even with antiviral medication, this infection has serious consequences for most infected infants.

While neonatal herpes is a serious condition, it is also very rare. Less than 0.1% of babies born in the United States each year get neonatal herpes. By contrast, some 20-25% of pregnant women have genital herpes. This means that most women with genital herpes give birth to healthy babies.

Understanding the Risk

Babies are most at risk for neonatal herpes if the mother contracts genital herpes late in pregnancy. This is because a newly infected mother does not have antibodies against the virus, so there is no natural protection for the baby during birth. In addition, a new herpes infection is frequently active, so there is an increased possibility the virus will be present in the birth canal during delivery.

Women who have genital herpes before they become pregnant have a very low risk of transmitting the virus to their babies. This is because their immune systems make antibodies that are temporarily passed to the baby through the placenta. Even if herpes is active in the birth canal during delivery, the antibodies help protect the baby. In addition, if a mother knows she has genital herpes, her doctor or midwife can take steps to protect the baby.

Herpes can also be spread to the baby in the first weeks of life if he or she is kissed by someone with an active cold sore (oral herpes). In rare instances, herpes may be spread by touch, if someone touches an active cold sore and then immediately touches the baby. Again, simple precautions can be taken to protect an infant from this type of exposure. To protect your baby, don’t kiss him or her when you have a cold sore, and ask others not to. If you have a cold sore, wash your hands before touching the baby.

Managing Genital Herpes During Pregnancy

If you’re pregnant and you have genital herpes, you may be concerned about the risk of spreading the infection to your baby. Be reassured that the risk is extremely small—especially if you have had herpes for some time. The following steps can help make the risk even smaller:

• Talk with your obstetrician or midwife. Make sure they know you have genital herpes.
• At the time of labor, your healthcare provider should examine you early in labor with a strong light to detect any sores or signs of an outbreak. Let your provider know if you have any signs of an outbreak—itching, tingling, or pain.
• If you have an active outbreak at the time of delivery, the safest course is a Cesarean section to prevent the baby from coming into contact with virus in the birth canal. If you do not have an active outbreak, you can have a vaginal delivery.
• Ask your provider not to break the bag of waters around the baby unless necessary. The bag of waters may help protect the baby against any virus in the birth canal.
• Ask your provider not to use a fetal scalp monitor (scalp electrodes) during labor to monitor the baby’s heart rate unless medically necessary. This instrument makes tiny punctures in the baby’s scalp, which may allow herpes virus to enter. In most cases, an external monitor can be used instead.
• Ask that a vacuum or forceps not be used during delivery unless medically necessary. These instruments can also cause breaks in the baby’s scalp, allowing virus to enter.
• After birth, watch the baby closely for about three weeks. Symptoms of neonatal herpes may include a skin rash, fever, crankiness, or lack of appetite. While these can be symptoms of several mild illnesses, don’t wait to see if your baby will get better. Take him or her to the pediatrician at once. Be sure to tell the pediatrician you have genital herpes.

Remember, the odds are strongly in favor of your having a healthy baby.

Treatment while Pregnant

Many women wonder about taking antiviral medication during pregnancy to suppress outbreaks in the third trimester. The U.S. Food and Drug Administration (FDA) has approved no drug against herpes for this purpose. Nonetheless, acyclovir is used by some physicians to treat women with genital herpes at the end of pregnancy. Small studies suggest that acyclovir taken daily during the last month of pregnancy will prevent recurrences and, therefore, decrease the need for Cesarean sections, but some experts remain concerned about the safety of fetal exposure to the medication.

At the present time, acyclovir’s manufacturer does not recommend its use during pregnancy. On the other hand, the company has tracked the experiences of several hundred women who took the drug during pregnancy, some of them inadvertently, and the evidence to date suggests that acyclovir does not carry increased risk of birth defects or adverse pregnancy outcome. On the strength of this data, the use of daily, suppressive treatment during the last month of pregnancy is becoming increasingly common.

Women who Don’t Have Genital Herpes

The greatest risk of neonatal herpes is to babies whose mothers contract a genital infection late in pregnancy. While this is a rare occurrence, it does happen, and can cause a serious, even life-threatening, illness for the baby. The best way you can protect your baby is to know the facts about HSV and how to protect yourself. The first step may be finding out whether you already carry the virus.

You can talk to your healthcare provider about testing for genital herpes. If you test negative for genital herpes, but your partner has genital or oral herpes, you may acquire it unless you take steps to prevent transmission. The following steps can help protect you from getting an infection during pregnancy:

• If your partner has genital herpes, abstain from sex during active outbreaks. Between outbreaks, use a condom from start to finish every time you have sexual contact, even if your partner has no symptoms. (HSV can spread when no symptoms are present.) Consider abstaining from sex (oral, vaginal, and anal) during the last trimester.
• Do not let your partner perform oral sex on you if your partner has an oral herpes (cold sores, fever blisters). This can give you genital herpes.
• If you don’t know whether your partner has genital HSV, you may wish to ask your partner to be tested.
• If you experience genital symptoms, or believe you have been exposed to genital HSV, tell your obstetrician or midwife at once. However, be aware that herpes can lie dormant for several years. What appears to be a new infection is occasionally an old one that is causing symptoms for the first time. Talk with your provider about the best way to protect your baby.
• When a pregnant woman does contract a new genital HSV infection during the last trimester, many providers will prescribe antiviral medication. If lesions or prodromal symptoms are present at the time of labor, a Cesarean section is the safest course to prevent the baby from coming into contact with virus in the birth canal. If the infection is acquired late in pregnancy, many providers would recommend a Cesarean section even without lesions present.