Genital herpes is a sexually transmitted infection (STI) that can cause serious health problems in infected newborns. Approximately 45 million Americans have genital herpes. Up to 1 million new cases occur each year, including about 1,200 to 1,500 in newborns.
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.
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.
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. 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.
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. 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.
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. A vaginal delivery is safe for most women with recurrent herpes as long as they don’t have signs of infection at delivery.
To learn more about signs and symptoms, health issues of the newborn and ways to try to prevent herpes transmission, read our fact sheet on genital herpes and pregnancy.