Pregnancy

Fifth Disease and CMV: Exposures in Pregnancy

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Exposure to fifth disease (parvovirus B19) or CMV in pregnancy is usually low risk, and the first step is telling your prenatal clinician. Many adults are already immune, and a blood test can confirm it. If you are not immune and become infected, ultrasound monitoring is used because serious problems are uncommon.

Last updated: July 2026

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What is fifth disease and how does it spread?

Fifth disease is a common childhood illness caused by parvovirus B19. It often starts with mild cold-like symptoms, then a bright red slapped-cheek rash on the face, sometimes followed by a lacy rash on the body; adults may instead get joint aches. The virus spreads through respiratory droplets, which is why outbreaks sweep through daycares, preschools, and elementary classrooms — much like hand, foot, and mouth disease. A child is usually most contagious in the 5 to 10 days before the rash and is generally no longer contagious once it appears, about 1 to 2 weeks after exposure. That timing is why pregnant teachers and parents often learn about an exposure only after the fact, which is common and rarely cause for alarm.

How risky is an exposure during pregnancy?

Most exposures do not harm the pregnancy. More than half of adults — roughly 50% to 60% — are already immune to parvovirus B19 from a past infection, so a fresh exposure poses no risk to them or the baby. Because most people first meet parvovirus in childhood or adolescence, immunity built years earlier quietly protects many pregnancies later in life. Even among those who are not immune, only some — often cited as roughly 1 in 3 — become infected, and most of those pregnancies continue normally. When infection does reach the baby, the main concern is anemia, which is uncommon and usually treatable when caught early; risk is greatest before about 20 weeks. According to prepregnancy guidance, checking immunity to infections is part of that counseling, so your history may already offer clues 1.

What will your prenatal team do?

Telling your prenatal clinician about the exposure sets a simple plan in motion. A blood test can show whether you are already immune (past infection), recently infected, or not immune, which determines the next steps. Prenatal care already includes routine blood tests and, when there is a concern, extra ultrasounds to check on the baby 2. If testing suggests a recent infection, clinicians typically schedule weekly ultrasounds for roughly 8 to 12 weeks to watch for early signs of anemia. Guidelines describe a schedule of antenatal checkups — about 10 in a first pregnancy — where a new worry like this can be raised, and scheduling that visit is a good first move 3. In most cases, monitoring shows everything is fine.

What about CMV and other daycare viruses?

CMV (cytomegalovirus) is another virus common in young children and worth understanding. It often spreads through saliva and urine, so contact with a toddler's drool, diapers, or shared food and utensils is the usual route. CMV is the most common infection passed to a baby in pregnancy, though most infected babies have no lasting problems. Because there is no vaccine, everyday hygiene — thorough handwashing after wiping noses and changing diapers, and not sharing food or cups with young children — is the main way to lower risk. Handwashing helps with parvovirus too. People planning pregnancy can review vaccines that are recommended to protect against other infections that do have shots.

When an exposure needs your prenatal team

Any infection exposure in pregnancy is worth a low-key call to your prenatal clinician, even when you feel well. Reasons to reach out promptly include a fever with a rash, joint aches with a known exposure, or feeling unwell after time around a child later found to have fifth disease or CMV. A noticeable drop in your baby's movements always warrants a same-day call. Testing and, if needed, ultrasound monitoring turn uncertainty into a clear plan, and most exposures end with reassuring results. Learning which medications are safe in pregnancy can help while you wait for answers. Gale can help you prepare for that conversation.

Common questions

The calm first step is to tell your prenatal clinician, who can order a blood test to check whether you are already immune. Most adults are, especially those who work with children. By the time a child shows the rash, they are usually no longer contagious, so the exposure risk is often lower than it feels. If you are not immune, your team will discuss monitoring.

In most cases, no. Even if you are not immune and become infected, the majority of pregnancies continue normally. The main concern is fetal anemia, which is uncommon and, when it occurs, is usually detected on ultrasound and can be treated. Risk is generally higher earlier in pregnancy, which is why monitoring is tailored to how far along you are.

Both are common in young children, but they spread and behave differently. CMV passes mainly through saliva and urine, while parvovirus spreads through respiratory droplets. CMV is the most common infection transmitted to babies in pregnancy, though most affected babies are healthy. Neither has a vaccine, so handwashing and not sharing food or cups with toddlers are the practical protections.

That depends on your immunity and situation, and it is a conversation to have with your clinician and possibly your workplace. Many immune adults need no changes at all. For those who are not immune, careful hygiene usually matters more than avoidance, since these viruses are widespread. There is no one-size-fits-all answer, so individual advice is worth getting.

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Pregnancy infection signs worth a prompt call

  • —A fever with a new rash during pregnancy is a reason to contact your prenatal clinician promptly.
  • —Feeling unwell after a known fifth disease or CMV exposure is a reason to seek clinician review.
  • —A noticeable drop in your baby's movements is a reason to call your maternity unit right away.
  • —Sudden swelling of the hands, face, or belly is a reason to seek urgent evaluation.
  • —Joint pain and a rash with a known exposure is a reason to ask your prenatal team about testing.

Call your maternity unit right away, or go to the nearest emergency room, if your baby's movements clearly drop, you develop a high fever you cannot bring down, or you feel seriously unwell.

This article is general health education, not medical advice. What an infection exposure means for your pregnancy is best assessed by your obstetric clinician or midwife, who can order the right tests.

References

  1. 1.American College of Obstetricians and Gynecologists (2019). ACOG Committee Opinion No. 762: Prepregnancy Counseling. Obstetrics & Gynecology. doi:10.1097/AOG.0000000000003013 ✓Guidance that checking immunity to infections is a routine part of prepregnancy and early-pregnancy counseling.
  2. 2.Office on Women's Health (U.S. HHS) (2025). Prenatal care. Office on Women's Health (womenshealth.gov), U.S. HHS. link ✓Overview of prenatal care, including routine blood tests and additional ultrasound monitoring when a concern such as an infection exposure arises.
  3. 3.National Institute for Health and Care Excellence (2024). Antenatal care (NG201). National Institute for Health and Care Excellence (NICE). link ✓Antenatal care guidance describing the schedule of antenatal appointments at which new concerns, including an infection exposure, can be raised and monitored.

3 sources, numbered by first appearance. General health information, not medical advice. AI-assisted editorial content — every citation independently verified. Editorial policy

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