How Rare Is Neonatal Herpes?
Let’s put some numbers on this right away, because they’re more reassuring than you might expect.
About 560 cases of neonatal herpes are reported in the US each year, out of roughly 3.6 million births. That’s about 1 in 6,000. Worldwide, the WHO estimates about 14,000 cases per year.
Is it serious when it happens? Yes, it can be. That’s exactly why it’s worth understanding. But the odds are overwhelmingly in your favor, especially when you know what to do.
How Would a Newborn Get Herpes?
There are three ways, and one of them accounts for the vast majority of cases:
During delivery (about 85% of cases). If the mother has active herpes lesions or is shedding the virus during vaginal delivery, the baby can come into contact with the virus in the birth canal.
After birth (about 10% of cases). This is the one that surprises people. Someone with an active cold sore can pass herpes to a newborn through a kiss or close contact. More on this below.
In utero (about 5% of cases). This is extremely rare, occurring in roughly 1 in 300,000 deliveries.
The Biggest Risk Factor (and Why It’s Probably Not You)
Here’s the part most people don’t realize: the biggest risk factor for neonatal herpes isn’t having a long history of herpes. It’s actually getting herpes for the first time during pregnancy, especially in the third trimester.
Why? Because when you catch herpes for the first time, your body hasn’t built up antibodies yet. Those antibodies are what protect your baby. If you’ve had herpes for a while, your immune system has already produced antibodies that cross the placenta and give your baby protection.
Here are the actual transmission numbers:
- First-time herpes infection, no prior antibodies: 25–60% transmission risk during delivery
- First outbreak of a new type (e.g., you have HSV-1, catch HSV-2): ~25%
- Recurrent herpes with visible outbreak at delivery: 2–5%
- Recurrent herpes with NO outbreak at delivery: less than 1%
That last number is the one that applies to most people reading this. If you’ve had herpes for a while and you don’t have an active outbreak when you go into labor, the risk to your baby is less than 1%.
Here’s another important fact: about 70% of neonatal herpes cases actually happen to mothers who didn’t even know they had herpes. It’s the undiagnosed first infections that are the most dangerous, not the people who already know their status and are taking steps to manage it.
What Does Neonatal Herpes Look Like?
If it does happen (and again, it’s rare), neonatal herpes shows up in three forms:
Skin, eyes, and mouth (about 45% of cases): Blisters on the skin, eye irritation, or mouth sores. This is the mildest form and responds well to treatment.
Central nervous system (about 30%): Affects the brain. Symptoms can include seizures, lethargy, and poor feeding. Usually shows up around 2 to 3 weeks after birth.
Disseminated (about 25%): Affects multiple organs. This is the most serious form. It can resemble sepsis in a newborn.
With early treatment (IV acyclovir), outcomes have improved dramatically over the years. Overall neonatal herpes mortality has dropped from over 20% to about 5% with modern high-dose acyclovir treatment.
How to Protect Your Baby
The good news: there are clear, proven steps that make neonatal herpes extremely unlikely.
If you have herpes
Your doctor will likely recommend daily antiviral medication starting at 36 weeks. This reduces the chance of an outbreak at delivery and lowers viral shedding. (This is straight from ACOG guidelines.)
If you have active lesions or prodromal symptoms when labor starts, a cesarean delivery is recommended. This is the single most effective way to prevent transmission during an active outbreak.
If you have no outbreak when labor starts (which is the case for most people on suppressive therapy), vaginal delivery is considered safe. You can read more about all of this in our herpes and pregnancy article.
If your partner has herpes and you don’t
This is actually the scenario that needs the most attention, because a new infection during pregnancy carries the highest risk.
- Use condoms throughout pregnancy, even when your partner has no symptoms
- Avoid receiving oral sex if your partner gets cold sores, especially in the third trimester
- Your partner may want to take daily suppressive therapy to reduce shedding
- Some doctors recommend type-specific blood testing for both partners early in pregnancy so you know exactly where you stand
The cold sore rule (for everyone around the baby)
This one is really important and it applies to anyone around your newborn, not just the parents. About 10% of neonatal herpes cases come from postnatal contact, often from someone with a cold sore.
- No kissing the baby if you have an active cold sore. Period. This goes for parents, grandparents, siblings, aunts, uncles, and visitors.
- Wash your hands thoroughly before holding the baby
- If you have an active cold sore, wear a mask when you’re near the baby
- These precautions are most important for roughly the first 6 weeks of life, when newborns are most vulnerable
I know asking Grandma not to kiss the baby feels awkward. But it’s a simple precaution that can make a real difference.
Breastfeeding
Breastfeeding is safe as long as there are no herpes lesions on your breast or nipple. If one side is affected, you can nurse from the other side while keeping the affected area covered. Herpes doesn’t pass through breast milk.
The Emotional Side
I know this article has some heavy information in it. Reading about risks and worst-case scenarios when it involves your baby is hard. So I want to bring it back to perspective.
If you know you have herpes, you are actually in a better position than someone who doesn’t know. You can take antivirals. You can communicate with your doctor. You can make informed decisions about delivery. You can take the cold sore precautions seriously. The people most at risk are those who have no idea they carry the virus.
You knowing is your superpower here. Your baby is going to be just fine. :)
