CMV is a common viral infection, especially among young children. Congenital CMV occurs when the infection is passed across the placenta from a pregnant woman to her developing baby. Some babies with congenital CMV infection show signs of disability at birth, while others are born healthy.
Pregnant women diagnosed with primary CMV infection should be referred for specialist follow-up.
Cytomegalovirus (CMV) is a common virus in the herpes virus family. Fifty per cent people have been infected by young adulthood and up to 85 per cent by 40 years of age.
Peaks of infection occur in children less than 2 years age, and during adolescence. Once a person becomes infected, the virus remains alive but usually inactive (dormant) within that person’s body for life.
It is rare for a person to get symptoms after the initial infection unless their immune system is weakened by severe illness and treatments (e.g. for cancer).
Reactivation can occur during pregnancy in women who have had infection previously, with a very small risk of transmission of CMV to the unborn baby.
Children and adults with healthy immune systems do not usually develop symptoms when infected, but may develop an illness similar to glandular fever with tiredness, sore throat, swollen glands and fever. People with a weakened immune system are more likely to develop symptoms.
Humans are the only source of CMV. The virus is found in urine, saliva, nasal mucous, breast milk, vaginal secretions and semen of infected people.
The risk of transmission from children born with disability due to CMV infection is no greater than that from children who have CMV infection without symptoms.
CMV is spread through:
If a woman is newly infected with CMV while pregnant, there is a risk that her unborn baby will also become infected (congenital CMV). Infected babies may, but not always, be born with a disability.
The highest risk to the unborn baby occurs when a woman who has never had CMV before is infected with the virus for the first time during pregnancy (primary CMV infection) and when infection occurs during the first half of the pregnancy. Infection during one pregnancy does not increase the risk for subsequent pregnancies. However, if primary infection occurs, consideration should be given to waiting for at least 12 months before becoming pregnant again.
Studies in Australia have shown that out of 1,000 live births, about 6 infants will have congenital CMV infection and 1-2 of those 6 infants (about 1 in 1000 infants overall) will have permanent disabilities of varying degree. These can include hearing loss, vision loss, small head size, cerebral palsy, developmental delay or intellectual disability, and in rare cases, death.
Sometimes, the virus may reactivate while a woman is pregnant but reactivation does not usually cause problems to the woman or her unborn baby.
There is no licensed vaccine against CMV currently available.
Pregnant women are recommended to take steps to reduce their risk of exposure to CMV and so reduce the risk of their developing baby becoming infected. Preventive steps include:
Child care workers who are pregnant or considering pregnancy should pay particular attention to good hand hygiene, especially after changing nappies or assisting with blowing noses or toileting.
A person who has been infected with CMV will develop antibodies in their blood that indicate infection has occurred, either recently, or in the past. These antibodies stay in the body for the rest of that person’s life. Other tests, that detect the virus, are used to determine if a person has an active CMV infection.
Testing for CMV is not routinely recommended for all women during pregnancy or for newborn babies. Testing for CMV should only be offered to pregnant women if they come into frequent contact with large numbers of very young children (eg child care workers).
Infants born to mothers diagnosed with a primary CMV infection during pregnancy should be tested for congenital CMV infection. Babies who do not have a normal hearing screening test at birth (SWISH) can also be tested for congenital CMV, as hearing loss is the most common sign of congenital CMV. However, some infants with congenital CMV infection who appear healthy at birth develop hearing or vision loss over time. For this reason babies known to be infected should have their hearing and vision assessed regularly.
Pregnant women diagnosed with primary (first) CMV infection should be referred for specialist follow up and counselling in order to receive up to date information about the risks and benefits of the available treatments, which are currently experimental.
Infants born with neurological disabilities due to CMV may benefit from early antiviral treatment; this should be discussed with a specialist paediatrician.
Most babies born with CMV infection grow up with normal health. Concerns about CMV infection can be discussed with a general practitioner or MotherSafe - a free telephone service that provides a comprehensive counselling service for women and their healthcare providers concerned about exposures during pregnancy and breastfeeding.
CMV infection is not a notifiable disease in New South Wales. Infection with CMV or congenital CMV does not affect access to school, work or childcare, including infants who have disabilities due to congenital CMV.
For further information please call your local Public Health Unit on 1300 066 055.
