When Carla Sobrini’s daughter Emilia failed her newborn hearing test, she had no idea that a virus she’d unknowingly caught from her older child during pregnancy was to blame.

By five weeks’ old, Emilia had failed a further two hearing tests – and a cheek swab showed she was positive for the common but little-known cytomegalovirus (CMV).

If a woman contracts CMV for the first time during pregnancy, it can cause deafness (through damage to the hair cells in the inner ear), blindness, brain damage and developmental delays and possibly autism in her baby in the womb.

Emilia now wears hearing aids – and when a blood sample taken during Carla’s first antenatal appointment at eight weeks was later tested, it showed recent antibodies to CMV, suggesting she had indeed contracted it early in pregnancy.

Yet if this blood sample had been tested for CMV at the time, Carla could have been given antiviral medication which reduces the risk of passing on the infection to the developing baby.

‘It was the worst day of my life when we found out I’d contracted CMV in the first trimester,’ says Carla, 38, who lives in north London with her husband Francesco, 49, who works in marketing, and their children, Leonardo, four, and Emilia, three.

Carla had never heard of the virus. Nor had she had any health problems during her pregnancy – ’I couldn’t remember feeling unwell and no one ever mentioned CMV in antenatal appointments’, says Carla, a director at an architecture firm.

CMV, which is one of the herpes simplex group of viruses (also responsible for cold sores) is usually harmless in adults and children, causing no symptoms (though some develop flu-like signs). However, there is a risk to babies within the first trimester, as their immune systems are not yet developed.

Carla Sobrini with her husband Francesco, son Leonardo and daughter Emilia - who was born with cytomegalovirus, leaving her with severe hearing loss

It’s transmitted via bodily fluids such as saliva and urine, and is mainly passed on by young children, due to poorer hygiene.

Carla believes she caught the virus from Leonardo, a baby while she was pregnant with Emilia.

She recalls: ‘I sucked Leonardo’s dummy, I used his cutlery, and I changed his nappies without washing my hands. They are things I could have easily avoided if I’d known about CMV.’

Around one in 200 babies in the UK is born with CMV and while most won’t have any symptoms, for around one in 1,000 – roughly 900 children each year – the impact is severe, says Lucy Liang, chair of the board of trustees at the charity CMV Action.

‘Yet despite being more common than Down’s syndrome, spina bifida or cystic fibrosis, CMV remains relatively unknown.’

There is no CMV screening for mothers during pregnancy, or as part of a newborn health check. The case against it has been concern that it would identify babies with CMV who would not have long-term problems as a result, but who could be put on antiviral treatment unnecessarily.

‘But we support CMV screening for all newborns,’ says Ms Liang. ‘In the UK, 25 per cent of preventable childhood hearing loss is caused by CMV. But sadly CMV screening, even after a failed hearing test, still isn’t always standard practice.’

A study published in JAMA Paediatrics in January found that when newborns in Canada were routinely tested for CMV (as part of the existing heel-prick blood test), many who’d been infected were identified, so were able to be treated and undergo monitoring by audiologists.

Lucy Liang, chair of the board of trustees at the charity CMV Action, says the impact of the virus is severe for around 900 children a year

Carla believes she caught the virus from Leonardo, a baby while she was pregnant with Emilia

If antivirals are given within the first month of life it can prevent hearing loss from progressing.

‘Treatment is critically important because the longer you can delay hearing loss, the better the brain is able to perceive sound,’ explains Paul Griffiths, an emeritus professor of virology at University College London.

The hearing loss can be progressive. ‘So if a child then becomes profoundly deaf and needs a cochlear implant [where electrodes are threaded into the cochlea, in the inner ear, to do the job of the damaged hair cells], their brain can still receive those signals and they can hear normally. But they need two years with their brain processing some sound in order to do this.’

Antiviral treatment doesn’t have much benefit if taken after becoming one month old, he adds.

In 2023, guidance from the National Institute for Health and Care Excellence recommended that all pregnant women should be told about the risks of CMV infection at their first antenatal appointment.

‘However, we still see significant gaps in healthcare training and awareness, and many families only hear about CMV after a diagnosis,’ says Ms Liang.

Professor Hermione Lyall, a consultant in paediatric infectious diseases at St Mary’s Hospital in London, adds: ‘It’s frustrating that women aren’t warned about CMV – especially when they are told to avoid cat litter due to the risk of toxoplasmosis infection, for example, or soft cheese in case it’s contaminated with Listeria bacteria.

‘Yet there are only a handful of babies affected by those things yearly in the UK.’

If pregnant women knew about CMV, she adds, and took steps to prevent catching it – such as not kissing their toddlers on the lips, washing their hands after changing nappies and not finishing off their children’s food – it would reduce the risk to babies altogether.

And if they do catch CMV, having antiviral treatment during early pregnancy could be effective – but without routinely screening pregnant women, it’s difficult to know who has been infected because they usually won’t have symptoms, or symptoms could be caused by another virus such as a common cold, says Professor Griffiths.

In some countries, such as France, expectant mothers have monthly serology tests (which test CMV antibodies) until the 20th week of their pregnancy.

‘This is the best way to reduce the risk of transmission,’ says Professor Lyall.

Newly-pregnant women could order a serology kit online, or ask their GP for one to identify their risk of transmitting the virus, she adds.

‘CMV affects entire families’ lives,’ says Ms Liang. ‘Parents tell us how terrifying it is not knowing if, or when, their child might lose their hearing or show signs of developmental delay.’

Nancy Taylor, 35, a personal assistant from Chelmsford in Essex, knows this all too well.

Her son Otis, now one, was born with CMV after she caught it from her daughter Ava, four. An MRI of Otis’s brain after birth showed mild inflammation and Nancy and her husband Alex, 30, an insurance broker, were told he might have learning challenges or develop autism.

Otis was given antiviral medication at nearly four weeks old.

‘It’s a waiting game,’ says Nancy. ‘His hearing and development so far are fine, but he’s not out of the woods yet.’ Developmental delay usually manifests by age five or six.

‘I’m teaching Otis sign language because I know of children born with CMV who suddenly lost their hearing aged four,’ says Nancy.

Meanwhile, Emilia has worn hearing aids in both ears since she was two months old – but her deafness has gradually got worse as more of the delicate hairs in the cochlea that relay sound waves have been affected and she’s on the verge of needing a cochlear implant.

What makes matters worse is that there were missed opportunities to diagnose Emilia sooner.

At birth, for example, her face was covered in small red spots, known as petechiae – a common sign of CMV in babies – and instead of being tested for CMV after failing one hearing test, Emilia was only tested after failing three. 

This meant she was seven weeks old when she started the antiviral treatment, past the point when it’s most effective.

‘Our world exploded when we were told Emilia had CMV,’ says Carla. ‘It felt like I was drowning.’

‘After that, everything she did was a question mark – was this normal or damage caused by CMV? When she started hitting her milestones, such as crawling or laughing for the first time, we started to relax. But this could have all been avoided if women were warned of the risks – we have a right to know.’

For more information visit cmvaction.org.uk