Herpes simplex virus, or HSV, is a virus that can cause sores and blisters in either the mouth or the genital area (and occasionally other body parts). Some research has tied herpes simplex virus to miscarriage, but the biggest risk of active herpes during pregnancy is that the baby could become infected during birth.
As background, HSV comes in two main form, HSV-1 and HSV-2. Doctors used to think that HSV-1 caused only cold sores (oral herpes) and HSV-2 genital herpes, but they now know that both virus types can cause both types of herpes. Between 50 and 80% of all adults carry oral HSV and about 1 in 4 have a genital HSV infection, although it may be inactive. Most people who are infected are not aware of it, since many people rarely or never develop the characteristic blisters. HSV cannot be cured, although it can be controlled and may become dormant.
Despite HSV being a very common infection, doctors don't believe that the virus causes miscarriages in most cases. Some research shows that women with unexplained recurrent miscarriages seem to be statistically more likely to have an undetected HSV infection than are women with no history of miscarriage, but there aren't any explanations for what that means and whether the virus actually plays a role in causing miscarriages for those women. Most women who are infected with HSV do not have recurrent miscarriages, so doctors need to conduct more research on the matter.
Similarly, a few researchers have found evidence that the virus could cross the placenta and lead to damage of the placenta (potentially increasing the risk of late pregnancy loss), but doctors don't understand what factors cause this to happen, given that the majority of infected women do not have this problem.
Thus, the biggest risk of having an active genital herpes infection during pregnancy is that the baby could acquire the infection during delivery, which could lead to serious health complications or death. Doctors may suggest a Caesarian section for women with active herpes who are about to give birth, and they may prescribe antiviral medications to women with a history of genital herpes infection in order to prevent an outbreak.
The risk of the baby being infected at birth is much higher for pregnant women who acquire genital herpes for the first time in their third trimester of pregnancy than for women who have been previously infected, so it is very wise to take continue to practice safe sex during pregnancy. If you suspect that you have herpes symptoms and you are concerned, the best thing to do is to talk to your OB/GYN or midwife about your concerns. But merely having a history of herpes shouldn't be any reason why you can't have a healthy pregnancy if you follow your doctor's advice.
Sources:
Avgil, Meytal and Asher Ornoy, "Herpes simplex virus and Epstein-Barr virus infections in pregnancy : consequences of neonatal or intrauterine infection." Reproductive Toxicology 2006. Accessed 14 Sept 2008.
March of Dimes, "Genital Herpes and Pregnancy." Quick Reference: Fact Sheets Mar 2005. Accessed 14 Sept 2008.
Naib, Zuher M., Andre J. Nahmias, William E. Josey, and Jenette H. Wheeler, "Association of Maternal Genital Herpetic Infection with Spontaneous Abortion." Obstetrics & Gynecology 1970. Accessed 14 Sept 2008.
New York State Department of Health, "Herpes Simplex Virus in the Newborn." Jun 2006. Accessed 14 Sept 2008.
Royal College of Obstetricians and Gynecologists, "Management of Genital Herpes in Pregnancy." Green-top Guideline No. 30 Sept 2007. Accessed 15 Sept 2008.
Zaki, Maysaa El-Sayed and Hossam Goda, "Relevance of Parvovirus B19, Herpes Simplex Virus 2, and Cytomegalovirus Virologic Markers in Maternal Serum for Diagnosis of Unexplained Recurrent Abortions." Archives of Pathology & Laboratory Medicine Jun 2007. Accessed 14 Sept 2008.
