CMV is a Common Cause of Birth Defects But Rarely Discussed

It’s the number one infectious cause of birth defects in the US, yet 91% of women have never heard of cytomegalovirus (CMV).

“I had no idea that I contracted [CMV] While I was pregnant,” says Laura Sweet, a parent advocate who works closely with the National CMV Foundation. “My daughter, who is amazing and is now 7, was born with congenital CMV, so she is deaf. As a result, she’s had two cochlear implant surgeries and she uses those devices to hear now. The virus also caused damage to her brain and one of her eyes.”

A baby is born with CMV infection every 30 minutes. In healthy adults and kids, it may just cause a mild illness, much like the common cold—if it shows symptoms at all. But if you happen to get CMV during pregnancy, you could unknowingly pass the virus on to your unborn baby, which can cause long-term health problems in 1 in 5 infants, such as hearing loss, vision impairment, cerebral palsy, learning disabilities and decreased muscle strength and coordination.

“We spent the first years of [our daughter’s] Life with weekly and early intervention appointments and services that really made a wonderful difference for her. She worked really hard and is incredibly determined. And thanks to that, she’s doing really well now,” Sweet tells Motherly.

But why is it so rarely discussed? Sweet says she now knows that she had a lot of risk factors for CMV when she was pregnant, but that none of her healthcare providers ever mentioned CMV or what she could do to try and reduce her risk. The American College of Obstetricians and Gynecologists (ACOG) used to encourage OB-GYNs to counsel pregnant women on CMV prevention, The New York Times reports, but then reversed course in 2015, stating, “Patient instruction remains unproven as a method to reduce the risk of congenital CMV infection.”

Because no real intervention efforts, like medication or a vaccine, were available, ACOG instead suggested that doctors should focus on educating patients about conditions with proven interventions.

Now, an antiviral medication exists that can help treat CMV infection in infants, and a CMV vaccine is currently being tested in a Phase III clinical trial by Moderna. But we still need better education for pregnant women, and some experts are pushing for a first-trimester pregnancy screening test (as is common in Europe) and universal screening tests for newborns, too.

Here’s what you need to know about reducing your CMV risk during pregnancy—and how to bring it up with your healthcare providers.


CMV is part of the herpes family, and infects most people at some point in their lives. “More than 50% of adults in the US will have been infected with cytomegalovirus (CMV) by age 40,” says Allison August, MD and VP of Medical Affairs at Moderna. But infection may not always present with symptoms, even in infants, which is what makes it hard to diagnose.

In adults and kids, if symptoms do appear, they are typically similar to the common cold:

  • Fever
  • So throat
  • Fatigue
  • Swollen glands

Occasionally, CMV can cause mononucleosis or hepatitis (a liver condition). More serious symptoms can be seen in kids and adults who are immunocompromised. Like other herpes family viruses, CMV can remain dormant in your body for years and become reactivated at a later date.

In newborns exposed to CMV with what’s known as congenital CMV infection, the following symptoms may sometimes be seen at birth:

  • rash
  • Jaundice (yellowing of the skin or whites of the eyes)
  • Microcephaly (small head)
  • Low birth weight
  • Hepatosplenomegaly (enlarged liver and spleen)
  • Seizures
  • Retinitis (damaged eye retina)

About 10% of infants with congenital CMV will show symptoms, but these symptoms can also be related to other conditions, so a urine or saliva test can be used to confirm a CMV diagnosis.

According to the CDC, some infants with signs of congenital CMV infection at birth can have long-term health problems, such as:

  • Hearing loss
  • Developmental and motor delay
  • Vision loss
  • Microcephaly (small head)
  • Seizures

Hearing loss may be present at birth, but not always. Some infants may pass the newborn hearing test and then become deaf later during the first year of life.


CMV is highly common in young children. By the age of 5, 1 in 3 kids has been infected with CMV, but usually does not have symptoms, notes the CDC.

And it’s highly contagious. CMV is typically transmitted through direct contact with shared bodily fluids, which may include coming into contact with the saliva, tears, breast milk, blood or urine of an infected person, and then touching your own eyes, nose or mouth.

CMV can also be transmitted to a baby during pregnancy, through birth or when breastfeeding.

It’s important to know also that the virus can shed in children’s body fluids for months after infection—which is why hygiene is incredibly crucial, especially if you’re pregnant.

“Simple hygiene methods such as good hand washing, not sharing food or drink or utensils, or avoiding sharing a pacifier in the case of a mom who is pregnant and might have a toddler at home can decrease your risk,” says Dr. August.

Risk factors

Parents and caregivers of young children are most at risk of CMV infection, which is why if you’re pregnant and already have a child under 5, it’s important to stay informed. But because it’s so widespread, it can affect anyone.

“There are certain communities that are disproportionately affected,” notes Dr. August.

“Communities of color and communities of lower socioeconomic status have a higher risk and burden of having children infected with CMV. In fact, if you’re a baby born in those communities, you have twice the risk of being infected with CMV.” The reasons why are multifactorial, she notes, but could be related to living in more densely populated areas.


If a baby is diagnosed with congenital CMV infection at birth, an antiviral medication (most likely valganciclovir) may be prescribed to help improve hearing and reduce long-term developmental impacts. However, valganciclovir can have serious side effects.

The CDC notes that it has only been studied in infants with signs of CMV infection, so it’s not safe for use as a preventive measure in other cases.


Moderna currently has a CMV vaccine candidate undergoing a Phase III clinical trial. A vaccine may help prevent CMV infection in pregnant women and infants and reduce the risk of an infant contracting congenital CMV.

The trial is ongoing, says Dr. August, and is being tested on women of childbearing age who are not currently pregnant. If you’re interested in being part of the trial, you can check your eligibility here.

In the meantime, good hygiene practices are the best prevention against CMV. Here are precautions to take, especially if you’re pregnant:

Wash your hands often. Aim to use soap and water for at least 15 seconds, especially after coming into contact with young children’s diapers, saliva or tears.

Avoid direct contact with a child’s tears and saliva. That may mean kissing your child on their head or forehead instead of on their lips.

Don’t clean your child’s pacifier by putting it in your mouth. You’re aiming to avoid contact with their saliva.

Avoid sharing food or utensils or drinking out of the same glass as others. Using the same straws or utensils—or toothbrush—can spread CMV.

Thoroughly clean toys, countertops and changing tables. Anywhere that could have come into contact with young children’s saliva or urine.

A note from Motherly

Learning about CMV can be distressing, especially if you’re currently pregnant and already worried about keeping yourself and your child safe from other infections or illnesses.

“Just don’t be bashful about getting educated about the virus and ways to decrease your risk of transmitting the virus,” says Dr. August. And don’t be afraid to ask your healthcare provider about CMV. Gathering the facts and learning about how to reduce your risk is a key part of staying healthy.

Featured experts

Allison August, MD, is VP of Medical Affairs at Moderna.

Laura Sweet is a parent advocate who works closely with the National CMV Foundation.

early pregnancy, giving birth, Health

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