Another infection that seems to have slipped under the radar is cytomegalovirus, which is disquieting as it is the commonest mother-to-child viral infection in pregnancy. A report recently published by the pressure group CMV Action revealed that only one in three adult women of childbearing age had even heard of CMV, yet as many as one in every 150 babies in the UK are born with the infection.

Between 50-80 per cent of adults in the UK are thought to carry CMV, which they probably picked up through the close contact of childhood. CMV is a virus that often doesn’t cause any symptoms, so the vast majority of carriers remain undiagnosed and, while it remains in the body for life, it is usually inactive and of no consequence.

However, the virus can be reactivated, usually when the immune system of the infected person becomes compromised, but sometimes because of a new infection with a different CMV strain. If the latter occurs, symptoms may appear, but because these are relatively non-specific – sore throat, fever and swollen glands are the commonest – it is often misdiagnosed as flu.

Regardless of how the virus reactivates, the sufferer is then said to have active CMV and is infectious to others. A pregnant woman with active CMV is at increased risk of miscarriage and stillbirth, and – assuming she carries to term – can pass the virus to her unborn baby, who is said to have congenital CMV. Often this is not an issue and the baby will be symptom-free.

However up to 1,000 babies born each year in the UK will have some form of damage as a result of the infection, and a similar number will develop problems later in life. While this number may not seem huge, it is worth noting that more babies are affected in this way than are born with Down’s syndrome. The symptoms of congenital CMV at birth can include jaundice, pneumonia, skin rashes, an enlarged liver and spleen, and seizures.

The newborn may also be of low birthweight and have a noticeably smaller head than anticipated (microcephaly). As the child develops, more problems often become apparent, ranging from visual impairment and epilepsy to learning difficulties and motor impairments such as dyspraxia.

The commonest effect is hearing loss, which can be in one or both ears, may be mild or total, and can worsen over time. This, in turn, often leads to difficulties with speech and communication. A neonate with congenital CMV is likely to stay in hospital longer than many other newborns and will be treated with antivirals.

Ganciclovir is the usual drug of choice, although it is highly toxic and therefore should only be prescribed by a specialist. An alternative is foscarnet but this is also highly toxic, depositing in teeth, bone and cartilage, and can cause renal impairment.

Once the baby is allowed to go home, regular hearing and eye tests will be necessary as well as close monitoring for other problems, particularly if organ function was not as expected at birth. The organisation CMV Action is pushing for health professionals to tell pregnant women about the virus and the impact it can have on maternal and child outcomes, and advise them of the steps they can take to reduce the chance of becoming infected. In much the same way mothers-to-be are routinely informed about the need to take folic acid supplements in order to reduce the risk of their baby developing a neural tube defect such as spina bifida.

Preventative measures include:

• Frequent handwashing with soap and water, particularly for those with other children still in nappies and individuals who work with young children
• Avoiding kissing children under the age of six years on the face, instead showing affection through hugs
• Not sharing food, drinks or eating utensils with young children to prevent ingestion of CMV-contaminated urine or saliva
• Using a barrier method of contraception when having sex during pregnancy.

A leaflet suitable for distribution to pregnant women, plus other resources on the condition, can be found here.