BLOG

Orly’s Question

Hey, welcome to our fifteenth “Mailbag: What does the Fox say?” Our first question is from Orly. Orly asked a question about parvovirus. “I’ve read that it’s dangerous for a pregnant woman to be around someone exposed to this virus, also known as fifth disease, or slapped cheek disease, or erythema infectiosum. One usually doesn’t know a child or individual has the virus until they develop a rash on their cheeks, and at that point, they’re no longer contagious. What are the risks for a fetus? Does it matter where one is in pregnancy when they’re exposed? And if they have antibodies for parvovirus, does it clear them from any adverse problems?”

Dr. Fox’s Answer

Alright. Great question, Orly. So, yes, parvovirus is the name of a virus, and children frequently contract it at a young age. It’s called fifth disease, like the number five, because traditionally, it was the fifth virus that they got, I don’t know exactly, probably going back 100 years or something like that. One of the symptoms is that, in addition to typical virus symptoms, such as fevers, they also develop a rash on their face that resembles a slapped cheek, characterized by red cheeks. Now, parvovirus itself is not usually a particularly dangerous infection for children or adults. Adults can get it too. Usually, in adults, it’s even less severe than in children. And so, it’s not an infection that we typically worry about from a medical perspective, whether for children or adults.

Parvovirus can be particularly dangerous for individuals with certain immunocompromised conditions. So, people with chemotherapy, HIV, whatever it is. So, that is something that could potentially be an issue. Now, in pregnancy, it can be an issue, and I’ll explain why. So, parvovirus is one of the few viruses that pregnant women contract that can directly affect the fetus. So, for example, a common cold, right? So, the mother might be, you know, a little bit under the weather, a little bit sick. The cold does not infect or hurt the baby. Even the flu, right? So, when pregnant women contract the flu, and we administer flu vaccines and worry about the flu, it’s not because we’re directly concerned about the flu harming the baby. It’s because pregnant women are all a little bit immunocompromised. Their immune system is slightly lower, so when pregnant women contract the flu, they can become much sicker than non-pregnant individuals. So, we do worry about the flu, but it’s really for the mother’s health.

When COVID came around, there was a big concern that it would infect and affect the fetus. That seems highly unlikely and unusual. However, COVID-19, like the flu, can be more severe in pregnant women, so we were similarly concerned, and we focused on vaccinations and other preventive measures. There are a couple of viruses that can, when contracted by the mother, even if she is not very sick, go through the placenta and infect and affect the fetus. But those are the exceptions. There’s one of them called CMV. One of them is Toxoplasma. Those two can potentially cause issues with organ formation. They can cause certain birth defects or can affect the development of the baby, potentially, in different organs.

Parvovirus is unique. So, parvovirus can travel through the mother’s body, via the placenta, to the baby; however, parvovirus does not cause birth defects or issues with the brain, heart, or other organs. But it can cause a very unique problem of fetal anemia. The parvovirus can affect a baby’s ability to produce red blood cells and cause fetal anemia. So, yes, we do get concerned if pregnant women are exposed to parvovirus, fifth disease.

Now, it turns out that many, if not most, adult women are already immune to parvovirus. So, parvovirus is one of those things that you typically would only get once in your life, sort of like chickenpox, right? Once you get it, or you’re vaccinated against it, you have antibodies against it. These are IgG antibodies, and you would not typically get it again. So, let’s say a pregnant woman is exposed to chickenpox. For the record, chickenpox is one of those viruses that is more of an issue for the mother getting sick than for the baby. However, if she’s exposed to chickenpox, we know she’s already immune to it because she has antibodies, so we typically don’t concern ourselves with her contracting chickenpox and becoming very ill.

So, for parvovirus, similarly, many, if not most pregnant women, will go into pregnancy already having been exposed to it, either when they were children, or some time in adulthood, or if they’ve had kids and got exposed from their other kids. And so they’ll have antibodies. Therefore, those women do not appear to be at risk of contracting parvovirus and infecting their baby. So, that’s not who we’re talking about. However, for someone who has never been exposed to parvovirus, never had it, and does not have antibodies, there’s a potential risk. If she were exposed to someone, usually a child, who has active parvovirus, she could, first and foremost, contract the infection. Number two, the infection can travel through the placenta to the baby and infect the baby. And number three, it could cause the baby to get anemic, which would be potentially dangerous to the baby.

So, from the point of someone saying, hey, I’m pregnant, and I was exposed to someone with fifth disease, with parvovirus, to the point of a baby being very, very sick, there are a lot of steps that would have to happen. So, for most, the vast majority of pregnant women who are exposed to someone with fifth disease, they won’t have any issues whatsoever, because, number one, they have to be someone who already does not have antibodies. So, either we’ll already know. In our practice, we usually routinely check for parvovirus antibodies at the beginning of pregnancy. Just in case this situation arises, we’ll already know if she’s potentially at risk of getting it. Therefore, it would have to be someone who does not already have antibodies, meaning they are at risk. Number two, she would have to contract the virus. Not everyone who is exposed to someone with the virus contracts the virus. So, if she’s someone who does not have antibodies, we will then check. Like, did she get ill? Does she have a fever? Did it seem like she had a viral illness? We can check a couple of weeks later to see if she now has antibodies, when she previously didn’t. This would indicate that she got infected between the first and second times we checked her antibodies.

So, that’s the second step: whether she may or may not actually contract the virus. And if she gets the virus, then what we do is check if there are any signs of the baby being anemic. And so, we do it with serial ultrasounds. We can also measure blood flow in a specific blood vessel in the baby’s brain. It’s called the middle cerebral artery. That blood flow pattern is a very good screening test for fetal anemia. We use it for other conditions where the baby’s at risk for fetal anemia, but for parvovirus, we do it specifically. And so, if she was exposed, and she got the virus, we do this weekly, for about two months, give or take, sometimes 10 weeks, because generally, if the baby’s going to get sick, it’s going to happen in that time period. And most of the time, nothing happens with the baby, or the test is mildly abnormal, but then it improves on its own, and the issue is resolved, leaving no cause for concern later.

There are times, a low percentage, where we do have someone who gets exposed to fifth disease, and they get the virus, and when we do the screen, the baby appears to be very anemic, and might be getting sick. And so, in that case, we would set them up for a fetal blood transfusion, which we can do. There’s a procedure where basically, it’s like an amniocentesis, where we take a sort of long needle, and it goes through her belly and into the uterus. But then we guide the needle into the umbilical cord, which is like the baby’s blood vessel, and we can, A, draw out blood, to double-check how anemic the baby is, and B, infuse blood into that cord, into the baby, and do a transfusion. Usually, for parvovirus, since it’s a temporary infection for the baby, meaning the baby clears it after time, we would only have to do this once. Again, for most people exposed to parvovirus, they have no risk whatsoever because they’re already immune to it. Even for people who are at risk of getting parvovirus, because they don’t have antibodies, if they’re exposed, they either won’t get infected, or if they do get infected, the baby won’t get anemic, or if the baby does get anemic, it’ll be mild, and not need treatment. And if it does progress to the point where it becomes severe, a treatment is available.

So, what ends up happening, practically, is that if someone calls our office and says, “Hey, I think I was exposed to parvovirus,” we’ll first go back and check: does she have antibodies preceding this exposure to parvovirus? If the answer is yes, we say, “Don’t worry about it. You’re already immune. You’re good to go.” If she doesn’t, we’ll say, “Okay, let’s check your antibodies again, see if they’ve become positive,” and probably a week or two later, recheck it, to see if they’ve become positive. If she has no signs of an infection, and these antibodies never what we call seroconvert, meaning they go from negative to positive, then even though she was exposed, she did not contract parvovirus, so she’s good. If, let’s say, it turns out she did get parvovirus, either it’s obvious because she got sick, or it’s evident because of the blood testing, the antibodies change, then we will do the weekly ultrasounds, for about 8 weeks or so, sometimes 10, from the point of her getting exposed and infected. And then, if nothing happens and they’re normal, she’s done. And if there are abnormal findings based on how severe it is, we’ll decide whether we’re just going to continue to watch closely and hope the baby recovers on its own, or whether we need to do the fetal transfusion. However, parvovirus is very common; it’s always present, and we perform very few fetal transfusions for parvovirus each year. So, even though it’s a very common virus, it’s not that common that it ends up leading to this. And again, it does not cause direct birth defects or anything like that. It’s really just if it causes fetal anemia. All right. Orly, great question. Thank you.

Maternal Fetal Medicine blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!