How Herpes Affects Pregnancy

The Effect of the Herpes Simplex Virus on Mother and Infant

Pregnant woman reading book at home. Credit: Jessica Peterson / Getty Images

Because a woman has genital herpes, does not mean she cannot have children. Twenty percent to 25 percent of pregnant women have genital herpes. However, the herpes simplex virus does pose a risk to the unborn child in certain situations. Knowing more about the risks of genital herpes infections during pregnancy helps mothers-to-be and their partners make informed decisions to protect themselves and their child.

Herpes Simplex Virus Infections

The herpes simplex virus causes a variety of infections and has specific characteristics. The following give more information on the basics of herpes simplex virus infections:

Risk Factors for Infant Herpes Simplex Infections

The risk of transmitting the herpes simplex virus to a baby depends on several factors:

  • Exposure of the infant to herpes lesions during delivery
  • Whether the mother has antibodies to the herpes simplex virus
  • Whether the infant has time to acquire these antibodies before delivery

Transmission Rates for Infant Herpes Simplex Infections

To illustrate how an infant's risk changes based on the above factors:

  • A woman who experiences a first outbreak of genital herpes during the third trimester and who has not developed antibodies to the virus by the onset of labor has a 33 percent chance of transmitting the virus to her infant.
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  • On the other hand, a woman who experiences a recurrent outbreak of genital herpes, because she already has antibodies to the herpes virus and has passed them to her unborn child, has a 3 percent chance of transmitting the virus to her infant.

    Effect of the Herpes Simplex Virus on Mother

    Many women have been exposed to the herpes simplex virus and have developed antibodies to the virus, but may not have had an outbreak of genital herpes. During pregnancy, the immune system becomes less effective and these women may have a first outbreak. This type of outbreak carries the same risk as a recurrent infection for the infant -- less risk of neonatal disease than with a primary infection. About 80 percent of women who are infected with the herpes simplex virus will have a recurrence during their pregnancy. Pregnant women previously infected with herpes will have an average of 3 recurrences during pregnancy.

    Effect of the Herpes Simplex Virus on Infant

    In infants who are known to have a herpes simplex virus infection, only less than one-third have mothers who had ever had a herpes rash or a sexual partner with a herpes rash. Many neonatal infections occur because of viral shedding from the cervix without evidence of a rash, usually after a primary infection. Most cases of transmission of herpes simplex occur during labor and delivery. For every 10 neonatal herpes infections, 6 to 7 are acquired because the mother acquires an asymptomatic first outbreak. Transmission of the herpes simplex virus to a newborn (neonate) can have devastating effects. The extent of the herpes simplex infection can range from a rash on the skin to involvement of the eyes and mouth, to infection of the brain, to infection throughout the body. All infants suspected of having a herpes simplex virus infection should be treated with IV acyclovir. The length of treatment is determined by the body system involved in the infection.

    Herpes Simplex Type

    The herpes simplex type determines the risk to the infant. A primary or recurrent HSV-1 infection during labor is more easily transmitted to the infant but the disease is limited to the mouth, eyes, and mucous membranes. Primary infection with HSV-2 is more likely to affect the central nervous system causing seizures, meningitis, developmental delay, and death.


    Currently, all women who have an outbreak of genital herpes, primary or recurrent, should have a cesarean section to reduce the exposure of the infant to the herpes simplex virus.

    Treatment of Herpes in Pregnancy

    Current recommendations by the American College of Obstetricians and Gynecologists (ACOG) are to treat all primary outbreaks of genital herpes with antiviral medications, including primary outbreaks in pregnant women. The antiviral medications available to treat genital herpes are acyclovir, famciclovir, and valacyclovir. Acyclovir has the most data on the safety of use in pregnancy. A registry of over 1000 pregnant women who were exposed to acyclovir during early pregnancy suggests that acyclovir is probably safe as there were no increases in birth defects.

    Precautions for Pregnant Women Without Herpes

    While any woman who has never had herpes should be cautious about having sex with someone who might have herpes, pregnant women should take extra precautions in their third trimester including:
    • Avoid intercourse and oral sex with partners who have or you suspect have genital herpes.
    • Consider asking your obstetrician about HSV antibody testing
    • CDC. "Sexually Transmitted Diseases Treatment Guidelines, 2006." Morbidity and Mortality Weekly Report. 55(2006): 16-20.
    • Habif, Thomas. "Warts, Herpes Simplex, and Other Viral Infections" Clinical Dermatology, 4th Edition. Ed. Thomas Habif, MD. New York: Mosby, 2004. 381-388.
    • Rouse, Dwight, MD and Jeffrey Stringer, MD. "An appraisal of screening for maternal type-specific herpes simplex virus antibodies to prevent neonatal herpes". American Journal of Obstetrics and Gynecology. 183 (2000): 400-6.
    • Rudnick, Caroline, MD, Ph.D., and Grant Hoekzema, MD. "Neonatal herpes simplex virus infections". American Family Physician. 65 (2002): 1138-42.
    • Yeung-Yue, Kimberly. "Herpes simplex viruses 1 and 2." Dermatologic Clinics 20(2002): 1-21.