With up to one in three women infected with genital herpes -- called Herpes Simplex Virus 2 (HSV-2) -- it's one of the fastest-growing sexually transmitted diseases to date. But about 90 percent of women with herpes don't know it -- they either don't have symptoms, such as genital lesions (slit-like sores), or don't recognize them. This can be dangerous for moms-to-be, since they can transmit the virus to their baby during delivery. While neonatal herpes is uncommon, it can cause severe brain and central nervous system damage, developmental delays, and even death.

But there's good news. "Though neonatal herpes is a devastating disease, it can easily be prevented," says Zane Brown, M.D., professor of obstetrics and gynecology at the University of Washington, Seattle. Here's what you can do:

• Get screened. All women should request the blood test for antibodies to herpes during their earliest possible prenatal visit, says Dr. Brown. If you test positive, your doctor will likely give you an antiviral medication at 36 weeks to prevent an outbreak. Since you'll pass the protective antibodies to your baby, the the risk of transmission during delivery is small -- less than 3 percent. If you test negative, avoid any exposure to herpes (abstain from sex, use condoms, or have your partner tested) as the transmission risk is 40 to 50 percent for a first-time outbreak that occurs during the third trimester, before your body can build up antibodies to pass to the baby.

• If you have symptoms during labor, your doctor may perform a cesarean to prevent the virus from being transferred to the baby or avoid using invasive instruments (such as a fetal heart monitor) that can increase exposure to the virus by breaking the baby's skin.

• Tell your pediatrician if you've tested positive so she can monitor your newborn for signs of neonatal herpes (lethargy, poor feeding, or sores on the skin); the risks to your baby are lower with treatment. To learn more, call the National Herpes Hotline at 919-361-8488 or visit www.herpes.com.

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