The proper name for CMV is cytomegalovirus. It is a common infection which is part of the herpes family of viruses. Once a person is infected, the virus remains inactive in their body for the rest of their life.
Congenital CMV infection occurs when a mother who is infected with CMV passes it to the foetus.
What causes congenital CMV infection?
CMV is spread through bodily fluids including saliva, semen, blood, urine, vaginal fluids and breast milk.
Congenital CMV infection is caused when the infection gets passed on from mother to the foetus via the placenta. The placenta is an organ that connects the developing foetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply.
Most cases of congenital CMV develop when a pregnant woman is infected by the CMV virus for the first time during, or shortly before, pregnancy.
In some cases, a previously inactive CMV infection can reoccur during pregnancy as a result of the mother having a weakened immune system. The mother could also be re-infected with another strain of the CMV virus causing it to be passed on to her unborn baby.
In most cases where CMV is passed from a mother to baby, the virus does not cause any damage to the baby. However, if a large amount of the virus is spread to the baby, it can interfere with the baby’s normal development, resulting in symptoms and associated disabilities of congenital CMV.
It is estimated that one to four babies in every 200 will be born with congenital CMV.
What are the signs and symptoms of congenital CMV infection?
Around 90 per cent of babies born with congenital CMV experience no symptoms at birth. This is known as an asymptomatic congenital CMV infection.
A small number of babies with asymptomatic congenital CMV may develop some degree of hearing loss over their first few years of life. Loss of hearing can range from mild to total.
The hearing problems can affect just one ear (unilateral hearing loss) or can cause problems in both ears (bilateral hearing loss). Children with bilateral hearing loss are likely to experience difficulties with speech and communication as they get older.
One in 10 babies born with congenital CMV do have symptoms at birth. These include:
- jaundice – yellow-coloured skin and yellowing of the whites of the eyes
- a rash of small, purplish spots
- an enlarged liver and spleen
- a low birth weight
- seizures (fits)
- small size
- small head size
While some of these symptoms can be treated, some babies will develop long-term conditions as a result of the infection.
Up to 90 per cent of babies born with congenital CMV who have symptoms at birth develop one or more physical or mental disabilities. These include:
- hearing loss
- visual impairment
- learning difficulties
- lack of physical co-ordination
- epilepsy – a condition that affects the brain and causes repeated seizures
How is congenital CMV infection normally diagnosed?
Have a baby checked right away if they were not examined by a doctor shortly after birth and you suspect that the head is small or notice other symptoms of congenital CMV.
If it is thought that a newborn baby may have congenital CMV, the virus can usually be detected by examining a sample of their body fluids, such as their urine or blood.
A doctor will also perform a physical examination of the baby to see if it is experiencing any symptoms of the infection. They will look for abnormal breathing sounds indicating pneumonia.
How is congenital CMV infection normally treated?
Congenital CMV can be treated with antiviral medicines. These cannot cure a congenital CMV infection, but can slow its progress.
The most common antiviral medicines used in treatment is ganciclovir (brand name Cymevene).
Ganciclovir can cause several side effects. One of the main side effects is bone marrow suppression. Bone marrow is a spongy material found in the hollow centres of some bones. It contains special cells called stem cells, which produce other specialised cells including red blood cells (which carry oxygen around the body), white blood cells (which help fight infection) and platelets (which help stop bleeding).
If ganciclovir suppresses your bone marrow, these specialised cells may not be produced. This can lead to serious bacterial infection, increased bleeding and anaemia, which may lead to extreme tiredness.
It may be necessary to keep babies who are born with congenital CMV in hospital until their normal organ function, such as their liver function, returns. They will also need to stay in hospital if they are being treated with the antiviral medicine ganciclovir.
If a baby is diagnosed with congenital CMV infection but shows no symptoms, you should have their hearing and vision checked regularly. If the child starts to have hearing or vision problems, early detection can help their development.
Can congenital CMV infection be prevented?
If you are pregnant, you can take steps to avoid getting a cytomegalovirus (CMV) infection. You can reduce your risk of contracting the infection by:
- Washing your hands regularly using soap and hot water, particularly before preparing food, before eating, after close contact with children and after changing nappies.
- Avoiding kissing a young child on the face.
- Do not share eating utensils (forks and spoons) with young children, or drink from the same glass as them.
What happens next?
Possible vaccinations for CMV are being researched.
One possible vaccine is aimed at young women. The theory is that vaccinating women before they become pregnant could reduce the risk of congenital CMV.