CMV is a virus that is related to the chickenpox virus. It usually causes no symptoms. When they do occur, they are usually mild and include fever, tiredness, and muscle aches.  

The first time a person is infected with CMV is called a primary infection. Once a person is infected, the virus stays in the body and can reactivate later. This is called recurrent infection. A person can also become infected with a different strain of CMV. Most people will have had CMV by the time they are 40.   

A person can get CMV by contact with an infected person’s body fluids, including blood, urine, feces, and saliva. A common way that people are exposed to CMV is by caring for young children. CMV can also be passed during sex through contact with semen or vaginal fluid. 

Up to one-half of people of childbearing age have never been exposed to CMV and are susceptible to infection. Approximately 1% to 4% of them will become infected with CMV for the first time during pregnancy. A primary infection during pregnancy usually does not cause symptoms in the pregnant person.  

It’s also possible for someone who had CMV in the past to have either reactivation of the disease or become infected with a new strain of CMV during pregnancy.  

CMV is most concerning for the fetus if a person gets it for the first time during pregnancy. The likelihood that a primary CMV infection during pregnancy will cause problems for the fetus can be broken down as follows: 

• In 40% of cases, the virus will pass to the fetus (congenital CMV). 

• 10% to 15% of babies with congenital CMV infection during pregnancy will have problems such as jaundice (yellowing of the skin), skin rash, and an enlarged liver and spleen at birth. 

• 25% of babies with congenital CMV who have no symptoms at birth will develop complications by age 2 years that can include hearing loss, intellectual disability, seizures, and eye problems that can affect vision.  

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The severity of how the fetus is affected appears to be related to when the primary infection occurs during pregnancy. Severe illness is more likely in babies whose mothers experience primary infection during the first half of pregnancy. CMV infection is more likely to happen later in pregnancy than early in pregnancy: 30% happen in the first trimester vs 40-70% in the third trimester. 

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The risk of fetal infection is much lower (2% or less) when the person has a recurrent CMV infection during pregnancy. Very few babies born to people with recurrent CMV infection have symptoms at birth. Up to 8% of babies develop long-term complications of hearing loss, vision problems, and mild brain or nerve effects by age 2, and up to 14% may develop complications by age 5.  

Routine screening of all pregnant women for CMV infection is not recommended. Testing for CMV may be offered if certain findings are noted on a routine ultrasound exam. When findings suggest that testing is needed, a blood test can help determine if someone has a primary CMV infection and when the infection occurred. 

Amniocentesis is used to diagnose fetal infection prenatally. However, it cannot give any indication about the severity of the infection or how the baby will be affected. 

Unfortunately, no treatments have been shown to be effective in preventing or treating congenital CMV infection. Studies have not shown that use of antibodies against CMV improves fetal outcomes. Possible treatment options such as antiviral therapy have shown no benefit and have uncertain risks.

Good hygiene, such as regular hand washing and glove use, can lower the chance of becoming infected with CMV. These measures have been shown to minimize the risk of infection for people who care for children or work in settings with children.