Cytomegalovirus and pregnancy

Cytomegalovirus (CMV) is related to the herpes virus that causes cold sores and chickenpox. Once you have the virus, it stays in your body for the rest of your life.

CMV is common and your immune system usually controls the virus. This means it does not cause any symptoms and is usually harmless. Most people do not realise they have it. But if you have or catch CMV when you are pregnant there is a very small chance that you can develop a CMV infection, which you may pass to your unborn baby. 

When a baby is born with a CMV infection, it's known as congenital CMV. Congenital describes a condition that the baby is born with that they developed in the womb. 

How common is congenital CMV infection?

Around 2,400 babies each year in the UK are born with congenital CMV.

In most of these cases the virus does not cause any problems. But a small number of babies may develop long-term problems due to the infection. These may include:

• a low birth weight
• a smaller head than usual (microcephaly)
• seizures (fits)
• hearing problems in 1 or both ears
• problems with the eyes
• problems with the liver and spleen.

How could I catch CMV?

You can get CMV from close contact with someone who already has it. It is passed through bodily fluids, such as urine, saliva, blood, poo, mucus and tears.

This means you can catch it from kissing, during sex, or by sharing food cutlery.

Pregnant women who work closely with children or already have a young family are more at risk of getting CMV.

If you already have CMV, it will stay dormant (inactive) in your body for the rest of your life. CMV can only be passed on during pregnancy when it's ‘active’. The virus is active when:

• you get CMV for the first time – young children often get CMV for the first time at nursery
• the virus has "re-activated" – because you have a weakened immune system
• you've been re-infected – with a different type (strain) of CMV.

How can I avoid catching CMV during pregnancy?

There is no vaccine for CMV. But there are things you can do to prevent infection, such as:

• avoiding sharing cutlery, drinks or food with anyone
• avoiding kissing babies, toddlers and small children on the mouth
• washing your hands with soap and water, especially after feeding babies and young children, changing nappies, touching dummies, or wiping noses  
• regularly washing toys or any other items that may have young children’s saliva or urine on them with soap and water.

Your midwife will give you information about how to protect yourself against CMV at your first antenatal appointment (the booking appointment).

Will I be tested for CMV as part of my routine antenatal care?

The UK National Screening Committee has recommended against routine screening for CMV in pregnancy. This is because most babies with CMV are not affected. 

Newborn screening for CMV is also not recommended because most babies with CMV do not develop any health problems. There is also no way of knowing which babies will develop any long-term health problems.

Occasionally, a routine ultrasound scan CAN show signs that your baby may have CMV. If this happens, your healthcare team will offer to do a procedure called amniocentesis to check if your baby is infected.

During amniocentesis, a long, thin needle is inserted through your stomach (abdominal) wall, guided by an ultrasound image. This can be uncomfortable, but should not be painful. The needle is passed into the amniotic sac that surrounds your baby and a small sample of amniotic fluid is removed for analysis.

There are risks associated with this procedure. One of the main risks is miscarriage, which can happen in up to 1 out of every 200 women and pregnant people who have amniocentesis.

A midwife or doctor will speak to you about what the test involves and let you know what the possible benefits and risks are to help you decide if you want to have the procedure.

If the amniocentesis shows that your baby has CMV, you should have ultrasound scans every 2 to 3 weeks until your baby’s birth. You will also be offered a blood test to see if you have the infection.

What are the signs and symptoms of CMV in pregnancy?

If you have CMV you may not have symptoms. But some people get a mild illness with flu-like symptoms such as:

• a high temperature
• sore throat
• aching muscles
• skin rash
• feeling sick
• tiredness
• swollen glands.

Call your GP or midwife if you have these symptoms. They may arrange tests to find out if you've been infected with CMV.

The test will be able to tell if you have an active infection or if you carry the CMV virus from a previous infection. You may need more than one test. 

If blood tests show that you have CMV, you may have extra ultrasound scans to check your baby’s development during pregnancy.  

What treatment can I have for CMV in pregnancy?  

There is currently no recommended treatment for CMV in pregnancy. But recent studies have shown that antiviral treatments with a drug called valacyclovir may help to reduce the risk of transmission to your baby during pregnancy. Ask your doctor what treatment options may be open to you.

What are the signs and symptoms of CMV in babies?

Most babies with congenital CMV do not have any symptoms and most will not develop any long-term health problems.  

A few babies born with CMV will have symptoms at birth, such as:

• jaundice
• lots of little red spots (petechiae)
• swollen liver and spleen
• a small head (microcephaly)
• low birth weight.

Some children born with congenital CMV will go on to have long-term problems.

If your baby’s doctor thinks your newborn has CMV, they will carry out tests to check for the infection. These may include saliva or urine tests. These should be done by the time your baby is 3 weeks old, so treatment can start before they’re 4 weeks.

What treatment is available for babies with CMV?

Your baby may not need any treatment if CMV is not causing any symptoms.

If your baby does have symptoms they may be given antiviral medicine. Treatment weakens the virus and reduces the chance of serious problems, but it does not cure the CMV infection.

Your newborn may have to have the first stage of treatment in hospital so they can be closely monitored for any side effects. Treatment usually lasts around 6 months.

Babies born with congenital CMV may have tests to check their kidneys, liver, brain, eyes and hearing, and regular follow-up appointments until they're around age 5. 

Can I pass CMV to my baby through breastfeeding?

You can pass CMV to your baby through your breast milk. This will not harm them if they were born at full-term and are healthy. Their immune system will be strong enough to deal with the virus and they will not be at risk of hearing loss or developmental problems.

Some premature babies are more vulnerable to CMV and may develop a sepsis-like condition if they get it. But this can be treated and does not lead to hearing problems or other issues. Talk to your healthcare professional if you have any concerns about feeding your premature baby. 

More information and support 

If you’re looking for advice you can call the Tommy's midwives on 0800 014 7800 (Monday to Friday, 9am to 5pm), or email us at [email protected].

Be aware that we only have one line available and you may not always get through straight away. Please leave us a message with your contact details and we will call you back as soon as possible.