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Genital Herpes and Pregnancy

by Dr. H., Medical Director

Managing genital herpes during pregnancy is very important to the health of the soon-to-be-born infant. Infants exposed to the herpes simplex can experience brain infection, seizures, prolonged hospitalization, mental retardation, and death if the infection takes hold.  With such a frightening prospect for potential harmful or fatal effects on the baby, then persons who have genital herpes must give careful thought to the risks associated with childbearing when one or both future parents have genital herpes.

With that caution, though, the reader should be assured that the risk can be limited and virtually eliminated through careful family planning and thoughtful monitoring by a knowledgeable obstetrician.  Estimates range that as many as 50 million Americans, and possibly more, harbor herpes simplex virus in the genital area.  Yet, the actual incidence of herpes infection in the newborn is exceedingly low.

Approximately 1 in 2000 births in America in which the mother is infected with genital herpes may result in herpes simplex virus transmission to the infant1,2, with the potential for effects on the baby as mentioned above.  Results in other countries such as England reveal a much lower rate of transmission of the virus to the infant, as low as 1 in 65,000 births, and the rate is estimated to be 1 in 15,000 births in Japan2.  The reasons for these differences are not clear.

The greatest risk to the infant is in those pregnancies in which the mother develops her first genital herpes infection ever while pregnant2.  In those pregnancies the risk to the baby of catching herpes simplex while in the womb is as high as 30 to 50% if the mother has the first outbreak of genital herpes during the final three months of pregnancy.  This presents a very high risk to the baby, and it is a risk that can be avoided with careful attention.

Partners in which one of the partners has genital (or oral) herpes, who are planning to have children, and in which the future mother does not have genital herpes must be especially careful not to place the future mother in a situation in which she might develop a first infection with genital herpes while pregnant.  For example, if the future father has genital herpes but the pregnant mother does not, it would be very wise to consult with the obstetrician prior to engaging in sexual relations during the pregnancy.  Even condoms might not give satisfactory protection, as discussed elsewhere on this web site.  It is also well documented that a pregnant woman having sexual contact with a new intimate partner during her pregnancy puts herself at a much higher risk of contracting primary genital herpes, and thus seriously endangering the child2.

The reasons for the increased risk to the newborn if the mother has the new onset of primary genital herpes are threefold.  First, the patient sheds virus for a much longer period during primary herpes infections.  Second, more viral particles are excreted during a primary infection as opposed to a recurrent infection.  Finally, less antibody is transmitted from the mother to the baby during a primary infection as opposed to during a recurrent outbreak (this is called transferring “passive immunity” to the baby, which involves the transmission of antibody through the placenta from the mother to the baby)2.

Elsewhere on this website discussion is found concerning how often patients who have genital herpes experience symptoms.  It is now known that as many as 80% of patients contract genital herpes in an “asymptomatic” manner.  This means that the patient does not realize that he or she has contracted the disease.  Very often patients can be infected with genital herpes and never have symptoms.

When this fact is translated to the situation of a pregnant patient, this means that very often a woman who is pregnant does not realize that she has genital herpes.  Thus, between 50-70% of infants who do develop herpes simplex infections shortly after birth are born to women who are asymptomatic at the time of delivery2.

Historically the traditional way to protect the infant against catching herpes simplex during pregnancy is to deliver the mother by Caesarian section.  This is an operation in which the baby is removed from the mother’s womb by surgery on the abdomen.  This surgery of course bears the usual risks and recovery period of major surgery to the mother, including infection, responses to anesthesia, and blood clots.  However, given those concerns, using this surgery to protect the newborn from the risk of herpes infection seems a useful tradeoff.

In a small percentage of cases, though, it appears that the herpes virus is actually transmitted to the baby while the baby is still in the womb.  However, very few cases of “in utero” transmission have been documented.  One would expect that active disease would be present at the time of delivery, and this is very rare.  Apparently the infection usually occurs at the time of labor and delivery in the vast majority of deliveries.  Sadly, though, neither blood tests nor viral cultures performed shortly prior to delivery are reliable enough to always prevent infection of the baby2.

Infection of the newborn immediately after delivery and not by the vaginal delivery itself is apparently very uncommon.  However, cases have been documented of the transmission of herpes to the baby from an infected nipple area on the mother as well as from a cold sore on one of the parents or other family members2.  In this small percentage of cases due to transmission shortly after delivery, persons with cold sores on their mouths or herpes lesions on their hands have apparently played a part in transmitting the infection to babies3.  Obviously it is wise for concerned parents, as well as hospital personnel and family members, to take reasonable steps to be sure that they don’t have any herpes lesions that are active or dormant that might come in contact with the baby.

Herpes simplex infections are treated with acyclovir, or with one of its related drugs such as Valtrex or Famvir.  Evidence has emerged that acyclovir, and Valtrex (which turns into acyclovir in the bloodstream), are very safe during pregnancy.  It has not been associated with birth defects in excess of those found in mothers who are not taking acyclovir during pregnancy4.  Acyclovir has been shown to reduce viral shedding in excess of 50% in some patients4.  Likewise its efficacy in reducing herpes recurrences during pregnancy has been documented4.

Thus, some real hope is now on the horizon that in cases in which the pregnant mother’s status of having genital herpes is known, use of acyclovir may carry real benefit in preventing the virus from being transmitted to the developing.  In no circumstances, however, should a pregnant patient EVER medicate herself with any drug without the consideration and consent from her obstetrician.

Concerned parents in concert with a knowledgeable obstetrician reasonably should seek appropriate testing to determine whether either parent is a carrier of the herpes simplex virus.  If appropriate testing is not available locally, concerned parents or physicians can find resources available through this and other websites.

We strongly suggest that any persons who have genital herpes and who are considering childbearing should make careful plans in advance as to how to manage the disease during pregnancy.  Using good education, adequate testing, and appropriate medications where indicated, parents can rest certain in the knowledge that they too can join the millions of other parents who have genital herpes and who have safely and successfully delivered a healthy baby.

    1. Authors’ experience with medical therapy of herpes genitalis in pregnancy, Zarcone R, Fortuna G, Castagnolo A, Vicinanza G, Bellini P, Carfora E, Lizza R, “Minerva Ginecol” 1998 Mar;50(3):105-7, Istituto di Ostetricia e Ginecologia, II Universita degli Studi, Napoli.
    2.  Neonatal Herpes University of Washington Academic Medical Center, Children’s Hospital and Regional Medical Center, 1998
    3.  Neonatal herpes: diagnosis and management, Kohl S., presented at the American Academy of Dermatology. Mar. 21-26, 1997, San Francisco.
    4.  Prevention of perinatal herpes: prophylactic antiviral therapy? Scott LL, Clin Obstet Gynecol 1999 Mar;42(1):134-48 University of Miami School of Medicine, Department of Obstetrics and Gynecology



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