Most healthy children and adults infected with CMV have no symptoms and may not even know that they  have been infected. Others may develop a mild illness; symptoms may include fever, sore throat, rash and fatigue.

Other symptoms, such as swollen glands, liver or spleen, may sometimes be present. However, these can be symptoms of a wide range of conditions, not just CMV.  Always talk to your doctor or midwife if you have concerns.

A blood test can tell if you have an active CMV infection or have had a previous infection.  Doctors can diagnose a maternal primary CMV infection (catching CMV for the first time) by testing for Immunoglobin M (IgM) and Immunoglobin G (IgG) antibodies and performing an “avidity” test, which checks how tightly the IgG binds to CMV.  By analysing levels of these antibodies and the avidity test, an estimate of the timing of CMV infection can be made.  These results will be interpreted by a virologist, as they are not always straight-forward.  Sometimes your midwife or doctor may ask you to have further blood tests done a few weeks later to help interpret the results of your tests.  

The timing of CMV infection is associated with the risk that the baby will be affected by congenital CMV.  If CMV infection is contracted in the first trimester, the risk of long-term problems is estimated at less than 1 in 100 and the risk in the third trimester is negligible.  Whilst the risks in the later stages of pregnancy are thought to be very low, the studies that report these findings have only followed up infants for the first few years of life, and longer-term studies are yet to report.

As the risks are highest around conception and early pregnancy, it is particularly important that women planning pregnancy or in the early stages of pregnancy take particular care to reduce the risks of catching CMV.

Even if you have had CMV before, it is still possible to catch a different strain. It is therefore important for all pregnant women, and those planning a pregnancy, to follow simple hygiene precautions even if they have had CMV before – nobody is ‘immune’.

The UK National Screening Committee has recommended against routine screening for CMV in pregnancy. This is because most babies with CMV develop normally.  Also screening would only detect cases of primary infection and tests available at present are not able to diagnose secondary infection (infection with a new strain or reactivation of the original strain of CMV).

Being  diagnosed  with  CMV infection when you are pregnant can be very stressful. However, it does not necessarily  mean  that your baby has the virus, or that they will have problems associated with CMV. Of all the women who catch CMV for the first time during pregnancy, two-thirds of women will NOT  pass it to their unborn baby and most babies who do have CMV remain well.

However, all women who are diagnosed with CMV infection in pregnancy should have additional scans so that any signs of CMV in the fetus can be found. These may include small for gestational age growth, microcephaly (small head) or altered signals in the brain or bowel.  You may be offered an amniocentesis (taking some water from the sac around the baby) to see if your baby has been infected.  It is recommended that an amniocentesis should take place at least 6 weeks after maternal infection, and after 20 weeks of baby’s gestation. 

It is important to remember that even if the virus has been passed on to your unborn baby, around 4 out of 5 babies born with CMV don’t have any health problems at birth.

Congenital CMV can cause a reduction in the number of red and white blood cells and inflammation of the liver (hepatitis).

Congenital CMV can cause some distinctive changes to the brain which may affect your child as they develop. A brain scan can help doctors to diagnose congenital CMV infection and also consider whether treatment with anti-viral medication is appropriate. In some cases, it can help doctors to identify children who may be most at risk of developmental or hearing problems in the future. The doctor will decide on the most appropriate kind of scan (ultrasound, or MRI, or in some cases both) and discuss the results.

Hearing loss is one of the most common symptoms of congenital CMV. This test will be more detailed than the hearing screen carried out on all babies at birth and carried out by audiologist.

This is to check for any inflammation or scarring on the retina (the light sensitive layer of tissue in the back of the eye). Some children may also have visual impairment caused by a brain problem rather than an eye problem.