Young children with CMV can spread it to susceptible family members and other caretakers. When a pregnant woman becomes infected with CMV, she can pass the virus on to her fetus. In a minority of cases, infected newborns develop serious illness or lasting disabilities, or even die.

How is CMV spread?
CMV can be passed from person to person through contact with infected body fluids, such as saliva, urine, blood and mucus. It also can be transmitted sexually or from infected blood products.

Infected adults occasionally develop a mononucleosis-like illness, which can include symptoms such as sore throat, fever, body aches and fatigue. CMV can cause serious illness, such as pneumonia and sight-threatening eye infections, in individuals with AIDS and other disorders of the immune system and in organ-transplant recipients.

A woman can pass CMV on to her baby before birth, during delivery or through breastfeeding. However, babies who become infected during delivery or from breastfeeding rarely have any serious problems from the virus (1, 2).

How common are CMV infections among newborns?
CMV is the most common congenital (present at birth) infection in the United States (1). Each year about 1 percent of all newborns, or about 40,000 babies, are infected (2).    

How does congenital CMV infection affect the baby?
Fortunately most babies are not harmed by the virus. About 85 to 90 percent of babies who are infected with CMV have no symptoms at birth (1). However, about 10 percent of these babies develop one or more neurological abnormalities (such as mental retardation, learning disabilities or hearing or vision loss) during the first few years of life (1). Congenital CMV infection is a leading cause of hearing loss in children (3).

About 10 to 15 percent of infected newborns show symptoms of CMV at birth (1). Symptoms may include an enlarged spleen or liver, jaundice (yellowing of the skin and eyes) and a distinctive rash. Up to 20 percent of these babies die, and about 90 percent of survivors suffer from serious neurological defects, such as mental retardation (3, 4).

At present there is no effective treatment for congenital CMV. However, researchers are investigating whether an antiviral drug called ganciclovir may help babies with congenital CMV. Ganciclovir is used to treat adults with AIDS or other immune-system problems who have CMV-related eye infections.
 
Which women are at highest risk of passing CMV on to their babies?
A woman who contracts CMV for the first time during pregnancy has about a 40 percent risk of passing the virus on to her fetus (3, 4). A woman can pass CMV on to her baby at any stage of pregnancy. However, studies suggest that babies are more likely to develop serious complications when their mother is infected in the first 20 weeks of pregnancy (3, 4).

Like other viruses in the herpes family, CMV stays in the body after symptoms disappear. Occasionally the disease reactivates. However, only about 1 percent of fetuses become infected when their mother has a recurrent infection (1, 3). And when these babies do become infected, they rarely develop any serious CMV-related problems (1).

How is CMV diagnosed?
In adults, CMV usually is diagnosed with blood tests. If a pregnant woman has possible symptoms of CMV, her health care provider usually will do two blood tests, with the second test two weeks after the first (1). The blood tests look for rising levels of certain CMV-fighting antibodies. A woman usually is diagnosed with CMV if her antibody levels rise fourfold (1, 2).

In newborns, doctors diagnose CMV by identifying the actual virus in body fluids within three weeks of birth (2).

Can CMV be diagnosed before birth?
If a pregnant woman is diagnosed with CMV, her provider can test her fetus for the infection using amniocentesis. In amniocentesis, the doctor inserts a thin needle through the pregnant woman's abdomen to withdraw a small amount of amniotic fluid. The lab tests the fluid for CMV. This test is at least 90 percent accurate in determining whether or not the fetus is infected with CMV (3). However, it cannot tell whether a fetus has severe symptoms of the disease. For this reason, doctors also recommend an ultrasound examination to identify brain abnormalities and other signs that a fetus may be severely affected.

Is there treatment for CMV infection in pregnancy?
There is currently no treatment to prevent an infected woman from passing CMV on to her baby. Nor is there any treatment that is proven to prevent CMV-related complications in infected babies. However, researchers are investigating whether treating infected pregnant women with immune globulin (disease-fighting antibodies) can help prevent or lessen symptoms in their babies (5). 

How can a pregnant woman help prevent CMV infection?
Women can help reduce their risk of CMV by practicing careful hygiene. This is especially important for women with young children at home or those who work with young children (such as daycare workers). As many as 70 percent of children between 1 and 3 years of age who attend daycare may be giving off the virus and can pass it on to their families or caretakers (2). To help prevent CMV, pregnant women should:

• Wash their hands thoroughly after any contact with the saliva and urine of young children, including after changing diapers or picking up toys

• Carefully dispose of diapers and tissues

• Avoid sharing drinking glasses and eating utensils with young children

Pregnant health care workers who may be in contact with infected patients, including newborns, also should practice good hygiene. They should follow the universal precautions recommended in medical settings for handling potentially contaminated materials. Medical or daycare workers also may want to consider being tested before pregnancy to see if they have had CMV in the past. If they have already had CMV, they have little cause for concern during pregnancy. Routine screening for all pregnant women is not recommended (2).

Is the March of Dimes conducting research on CMV?
March of Dimes grantees and other researchers are developing vaccines that eventually may protect babies against CMV. One March of Dimes grantee is testing the effectiveness of a vaccine in protecting women of childbearing age from infection with CMV.  Others are seeking to learn more about this virus and how it multiplies and spreads in the fetus, in order to develop effective drugs that can help prevent birth defects in infected babies.

For more information
Read the fact sheet provided by the Organization for Teratology Services.

References
1. Centers for Disease Control and Prevention (CDC). Cytomegalovirus (CMV) Infection. Updated 9/12/05.

2. American Academy of Pediatrics. Cytomegalovirus Infection. In: Pickering L.K. (ed.) 2003 Red Book: Report of the Committee on Infectious Diseases 26th edition. Elk Grove Village, IL, American Academy of Pediatrics, 2003, pages 259-262.

3. Hollier, L.M. and Grissom, H. Human Herpes Viruses in Pregnancy: Cytomegalovirus, Epstein-Barr Virus, and Varicella Zoster Virus. Clinics in Perinatology, volume 32, September 2005, pages 671-696.

4. Duff, Patrick. Immunotherapy for Congenital Cytomegalovirus Infection (Editorial). New England Journal of Medicine, volume 353, number 13, September 29, 2005, pages 1402-1404.

5. Nigro, G., et al. Passive Immunization During Pregnancy for Congenital Cytomegalovirus Infection. New England Journal of Medicine, volume 353, number 13, September 29, 2005, pages 1350-1362.