CMV in Pregnant Women

A Virus that Poses Risks to Unborn Babies

Cytomegalovirus, or CMV, is the largest of all the herpes viruses and infects most people some time in their life. Most infections are harmless, but CMV can be extremely problematic in some circumstances. Transmission of the virus from pregnant women to their fetuses can cause permanent disabilities, and people with weakened immune systems can be at risk for severe disease. It is a leading cause of birth defects in the US.

It causes many more cases of birth defects than more commonly well known causes.

Name: Cytomegalovirus

Type of Microbe: DNA virus belonging to the herpesvirus family

How it spreads: CMV is spread through most body fluids, including saliva, tears, breast milk, blood, urine, semen, and vaginal fluids. Infected pregnant women can pass the virus to their unborn babies either during pregnancy or birth. Infection with CMV is lifelong, but the virus is usually only spread during initial infection, and most people do not show symptoms of an infection.

Who’s at risk? Almost all people get infected at some time in their life, but young children are more likely to transmit CMV than older children or adults. Pregnant women, who are most often infected after contact with saliva or urine of young children, can pass CMV to their fetuses in utero. Women can also have recurrence of infections; they may carry the virus from a prior infection, such as when they were children themselves.

 Children born with congenital CMV infections are at risk for developing permanent disabilities. People with weakened immune systems are also at risk for more severe disease. Pregnant women may also pass the infection during the birth process when babies are exposed to CMV from genital tract secretions or breast milk.

Symptoms: Most healthy people show mild or no symptoms. They may not know they have the virus. Mild symptoms may include fever, sore throat, and swollen glands. In a study of pregnant women who were diagnosed with a first case of CMV, most had flu-like symptoms, an elevated white blood cell count and mild liver inflammation.

The infection can also recur. You could get over a case of CMV but then have it reappear. This happens especially when people are sick and their bodies stressed, such as people who are hospitalized and very sick, such as in an intensive care unit.

Babies may be infected with CMV during gestation (congenital infection) or at delivery (perinatal infection). Approximately 10% of babies with congenital CMV will have immediate problems with the liver, spleen, or lungs, small birth size, purple skin splotches, seizures, or death. Of babies born with asymptomatic CMV infections, approximately 15% will develop eventual hearing loss. Babies who get CMV after birth (postnatal) are less severely affected and may have disabilities such as hearing or vision loss, as well as reduced cognitive ability. In postnatal and asymptomatic congenital CMV infections, some symptoms do not appear immediately, but only after months or years following birth.

The most common of these are hearing or vision loss, so it is important to regularly monitor your child’s hearing and vision if he or she was born with CMV.

Diagnosis: Most CMV infections do not get diagnosed because of the lack of symptoms. Blood tests are available for detecting the virus or antibodies in the blood or urine, but they are not routinely used. CMV testing is not recommended for pregnant women because the risk associated with the test (amniocentesis) outweighs the risk of spreading the infection to the baby. However, blood tests can be requested to detect the presence of antibody against the virus.

The presence of antibodies in the absence of a circulating virus usually indicates that you have already been infected and cleared the virus in the past and there is little chance of spreading it to your unborn baby. If you do not have evidence of a prior cleared infection, follow the prevention guidelines below to reduce the risk of infection by this ubiquitous virus.

Treatment: There is continuing research on treatments for CMV infections, including antibodies and antiviral medications. If you have a case of CMV during pregnancy, it is important to talk to your healthcare provider about what options are available then. Not all drugs that might work will work. This infection is treated regularly with antiviral drugs in patients with weak immune systems who get sick (such as transplant or cancer patients). However, because of serious side effects, these drugs may not be useful for pregnant women. Vaccines are currently being researched with the hope of having an easier way to prevent this common infection. 

Prevention: Good personal hygiene; frequent handwashing; limiting contact with saliva and nasal secretions from young children

Complications: Permanent disabilities associated with congenital CMV include hearing or vision loss, growth and developmental problems, seizures, and death.


Cytomegalovirus (CMV) Centers for Disease Control and Prevention.