Yes, a baby can be born with HSV-1. This is called neonatal herpes, and it happens when the virus passes from mother to child during pregnancy, labor, or shortly after birth. About 30% of neonatal herpes cases are caused by HSV-1, with the remaining 70% caused by HSV-2. While neonatal herpes is uncommon overall, it can be serious, so understanding how transmission happens and how it’s prevented matters.
How HSV-1 Passes From Mother to Baby
The virus can reach a newborn through several routes. The most common is direct contact with active herpes lesions in the birth canal during vaginal delivery. But HSV-1 can also cross the placenta during pregnancy through the mother’s bloodstream, traveling to the baby’s central nervous system and establishing itself there before birth. This blood-borne route has been confirmed in research showing the virus can colonize the fetal brain and later reactivate from a dormant state, just as it does in adults.
Transmission can also happen after delivery. A mother, father, or caregiver with an active cold sore (oral HSV-1) can pass the virus to a newborn through direct skin contact or even indirect contact, like kissing the baby’s face or hands. Because newborns have immature immune systems, an infection that would be harmless in an adult can become dangerous in the first weeks of life.
When the Risk Is Highest
The single biggest risk factor is a mother having her first-ever herpes outbreak during pregnancy, particularly near delivery. A primary HSV infection carries a transmission rate of roughly 50%. That’s because during a first infection, the mother’s body hasn’t yet produced the antibodies that help suppress the virus and protect the baby.
Recurrent outbreaks are far less risky. Mothers who already had HSV before pregnancy have circulating antibodies that cross the placenta and offer the baby some protection. The risk drops substantially, though it doesn’t disappear entirely, because the virus can still shed from the skin without visible sores. A first outbreak during the third trimester is especially concerning because there’s not enough time before delivery for the mother to build a strong antibody response.
What Neonatal HSV-1 Looks Like
Neonatal herpes is divided into three categories based on severity, and symptoms typically appear within the first few weeks of life.
- Skin, eye, and mouth disease (SEM): The mildest form. Babies develop small fluid-filled blisters on the skin, around the eyes, or inside the mouth. These lesions often appear earliest, sometimes within the first five or six days of life. SEM disease has the best outcomes when treated promptly.
- Central nervous system disease: About 30% of neonates with herpes develop this form, which affects the brain. The hallmark is herpes encephalitis, an inflammation of the brain that can cause seizures (in roughly 67% of cases), extreme sleepiness, poor feeding, irritability, a bulging soft spot on the skull, and abnormal muscle tone. Some babies may also have SEM lesions, but others show no skin signs at all, making diagnosis harder.
- Disseminated disease: The most dangerous form. The virus spreads to multiple organs, including the liver, lungs, and brain. Up to 60% of babies with disseminated infection also have brain involvement.
The early symptoms of neonatal herpes, fever, fussiness, poor feeding, and lethargy, look a lot like other common newborn illnesses. That overlap is one reason the condition can be tricky to catch quickly.
Long-Term Effects
Even with antiviral treatment, neonatal herpes encephalitis carries a mortality rate of 4 to 14%. Among survivors, 56 to 69% experience some degree of long-term neurological effects, which can include developmental delays, learning difficulties, seizure disorders, and motor impairments. Antiviral therapy has significantly improved survival rates compared to earlier decades, but varying degrees of brain damage still occur in a substantial number of children.
Babies with SEM disease who receive prompt treatment generally do much better, with lower rates of lasting complications. The key factor in outcomes across all three categories is how quickly treatment begins.
How Doctors Prevent Transmission
Prevention during pregnancy focuses on two strategies: antiviral suppression therapy and delivery planning. Mothers with a history of genital herpes are typically started on suppressive antiviral medication around 36 weeks of pregnancy. In one study, this approach reduced recurrent outbreaks at the time of delivery from 36% to 0%.
If a mother has active genital herpes lesions when labor begins, a cesarean delivery is recommended. This avoids the baby passing through the birth canal where the virus is shedding. For mothers who have their first herpes outbreak during the third trimester, a cesarean may also be offered even without visible lesions at the time of labor, because viral shedding can continue for weeks after a primary infection.
Testing Newborns at Risk
Babies born to mothers with a known first herpes outbreak during the third trimester are tested around 24 hours after birth, even if they look perfectly healthy and even if the mother had no visible lesions at delivery. Testing involves swabbing five sites: both eyes, the nose, the mouth, and the rectum. These swabs are combined into a single sample and analyzed using a DNA test that can detect tiny amounts of the virus. If there are visible blisters, those are swabbed directly. Spinal fluid is also tested using the same DNA method when brain involvement is suspected, since older culture-based tests miss too many cases.
Protecting Your Newborn After Birth
Postnatal transmission is a real and preventable risk, particularly from cold sores. The CDC advises that anyone with an active herpes lesion, whether on the lips, face, or elsewhere, should not kiss a newborn and should wash their hands thoroughly before holding the baby. Even a healing cold sore can shed virus.
Mothers with HSV can safely breastfeed as long as there are no lesions on the breast. If a lesion is present on one breast, that side should not be used for feeding, and any expressed milk from the affected breast should be discarded until the lesion heals completely. The unaffected breast remains safe for both direct nursing and expressed milk, provided the lesion on the other side is fully covered and hands are washed carefully. Pump parts should be cleaned thoroughly between uses.
These precautions apply to everyone in the household. HSV-1 is extremely common in the adult population, and many people shed the virus without knowing they’re doing so. During the first few months of life, keeping cold sores away from a baby’s skin is one of the simplest and most effective protections available.