What is CMV?

Cytomegalovirus, or CMV, is a common virus that can sometimes cause hearing loss. More than half of the people in the United States have had a CMV infection by the time they’re 40 years old. Many people are infected with CMV and don’t know it because it rarely causes symptoms or long-term problems.

However, CMV can cause problems in people who have weak immune systems and in newborns, such as hearing loss.

Is My Baby At Risk of Having CMV?

Yes, but the risk is very low. For every 100 babies born in the United States, 1 or 2 (1-2%) will have a CMV infection. If a woman has a CMV infection while she is pregnant, the CMV infection can be passed on to the baby.

How Do We Know If My Baby Has CMV?

First, we test your baby’s hearing. If your baby passes the hearing test, we don’t need to test your baby for a CMV infection.

If your baby doesn’t pass the hearing test, they will need to have a second hearing test and a CMV test before leaving the hospital.

Is My Baby At Risk of Developing Hearing Loss From a CMV Infection?

Your baby’s risk of having permanent hearing loss from a CMV infection is very low.

My Baby Didn't Pass the Hearing Test. Why Do They Need to Be Tested For CMV?

It’s important to test for CMV if your baby didn’t pass the hearing test because treating a CMV infection early can help prevent long-term hearing loss.

Other important reasons include:

  • CMV infections are the most common cause of hearing loss in children in the United States.
  • CMV infections can be harder to find and treat after your baby’s first 21 days of life.
  • If a woman gets CMV while she is pregnant, she can pass it on to her baby.

For every 100 mothers who have CMV while pregnant, 14 (14%) of them will pass it on to their babies. Out of those 14, 3-5 (3-5%) babies will develop hearing loss in 1 or both ears from a CMV infection.

How Do You Test For a CMV Infection?

We use a swab to gently wipe the inside of your baby’s mouth. We then test your baby’s saliva in our lab. Your baby’s primary care doctor will call you with the test results.

What Are the Possible Results From the Referred Hearing Test and CMV Test?

If the results are negative for a CMV infection, your baby will have frequent follow-up care with their primary care doctor.

If the results are positive for a CMV infection, we will talk with you about treatment options and follow-up care for your baby.

Who Can I Talk To If I Have Questions About CMV and Hearing Loss?

Your baby’s primary care doctor can answer any questions you have about CMV infections and hearing loss.

Rev. 8/2020. Mass General for Children and Massachusetts General Hospital do not endorse any of the brands listed on this handout. This handout is intended to provide health information so that you can be better informed. It is not a substitute for medical advice and should not be used to treatment of any medical conditions.