What is CMV?

Cytomegalovirus (CMV) is a virus that is common in adolescents and children under 2 years of age. It often doesn't cause any obvious symptoms, so you may not know you've been infected. About half the population have had CMV by age 18 years.

After you catch CMV, the virus stays in your body in an inactive form. It can become active again when your immune system is weaker than usual, such as when you're pregnant.

It's possible for an unborn baby to become infected with CMV, especially if you are infected for the first time while you are pregnant. This can sometimes cause serious problems for your baby.

How does CMV spread?

CMV is transmitted from person to person through contact with body fluids, such as saliva, nasal mucus, urine, vaginal discharge, semen and breastmilk. It can be spread by coughing and sneezing and by contact with objects that have body fluids on them. It's also possible to get CMV from having sex, a blood transfusion or an organ transplant. Babies can become infected with CMV during breastfeeding.

If your child has had CMV, the virus can continue to appear in their urine and saliva for years afterwards. It can infect other people who haven't had CMV, for example, by having contact with the child's toys, used tissues or nappies.

Congenital CMV

If you have CMV when you're pregnant, the virus can travel across the placenta and infect your baby. This is called congenital CMV.

This can happen if:

• it's the first time you've been infected with CMV (known as primary infection)
• you've had CMV before and the virus in your body becomes active again (known as reactivation)
• you get infected with a different strain of CMV than you've had before

You are more likely to pass the virus on to your baby if you have a primary CMV infection during pregnancy. CMV can spread to your baby at any stage of pregnancy, but risk is higher in the first half of pregnancy.

What are the risk factors for CMV in pregnancy?

People with young children at home and people who work in childcare centres are at higher risk of catching CMV if they haven't had it before.

What are the symptoms of CMV?

CMV usually doesn't cause any noticeable symptoms. In some people it can cause mild symptoms such as fever, swollen glands, tiredness, sore throat and a cough. Sometimes it can cause mild liver inflammation. These symptoms usually go away by themselves.

CMV can cause serious illness in people with a weak immune system, for example people with HIV or who are having chemotherapy for cancer.

Most people don't know they have CMV infection, or if they have had it before. You might find out from a blood test that you've had it.

How does CMV affect unborn babies?

Most babies born with CMV don't have symptoms or health problems as a result of the virus, but some do. Your baby is more likely to be affected you contract CMV for the first time during pregnancy. Your doctor might see signs of congenital CMV on a pregnancy ultrasound.

About 3 in 10 people who get CMV for the first time in pregnancy will pass it on to their baby. Of these babies, about 1 in 10 will be born with symptoms. In total, about 1 or 2 out of every 10 babies infected with CMV during pregnancy will have a long-term health problem.

If your baby is born with symptoms of congenital CMV, these may include:

• rash
• small head size
• enlarged liver and spleen
• pneumonia
• low platelet count

Congenital CMV also increases your baby's risk of poor growth, miscarriage, stillbirth and death before 3 months of age.

If your baby is born without symptoms, there's a chance they could develop health problems later. These may include:

• poor hearing — this is the most common problem
• poor vision
• intellectual impairment
• developmental delay
• cerebral palsy
• seizures

Babies who are born without any obvious symptoms or hearing loss have a lower chance of problems.

If your baby has abnormal hearing test results, your doctor may also recommend testing for CMV.

How common is CMV in pregnancy?

Most adult females have been exposed to CMV in the past.

How is CMV diagnosed in pregnancy?

There is a blood test to check for CMV, but in Australia it's not routinely recommended in pregnancy. CMV testing in pregnancy is recommended for:

• people who develop symptoms of a viral infection that suggests CMV
• people who come into frequent contact with young children (such a healthcare or childcare workers)
• people who know they have been exposed to someone with a new CMV infection
• people who have had a pregnancy ultrasound that shows signs of congenital CMV

You can check with your doctor if you should be tested for CMV. If testing shows that you have CMV, your doctor may recommend more tests to see if your baby has CMV too. It's important to remember that most unborn babies who test positive for CMV during pregnancy will not have long-term complications.

If you have CMV during pregnancy, your baby should be tested for CMV after birth.

If you are concerned about CMV testing, speak to your doctor.

How is CMV treated during pregnancy?

Research is ongoing, but currently there's no treatment that clearly lowers the risk of your unborn baby catching CMV during pregnancy. If you are concerned, it's best to discuss this with your doctor.

If your baby tests positive for CMV, your doctor may recommend regular hearing tests and eye checks to identify any issues early.

Can CMV be prevented?

There is currently no vaccine to prevent CMV infection, and no way to ensure prevention. The best way to reduce your chance of infection with CMV is by practising good hygiene. Try to reduce your chance of contact with body fluids that may be contaminated with CMV.

If you are pregnant, it is a good idea to:

• regularly and thoroughly wash your hands with soap and water, particularly when feeding and caring for children, changing nappies, wiping noses or handling anything contaminated with body fluids
• regularly clean surfaces and objects that may have body fluids on them
• wear gloves when changing nappies
• avoid kissing children on the lips or putting dummies in your mouth
• avoid sharing food, cups, utensils, or toothbrushes

If you have any concerns, you can discuss them with your doctor or midwife.

Resources and support

For more information about CMV and its transmission and symptoms, as well as congenital CMV, see the Sydney Children's Hospitals Network website.

For more information about CMV in pregnancy including prevention, symptoms, diagnosis and management see the NSW Health website.

Call Pregnancy, Birth and Baby on 1800 882 436 for advice, support and guidance from our maternal child health nurses.