CMV in pregnancy: cytomegalovirus, risks to your baby and how to lower them

CMV (cytomegalovirus) is very common and usually harmless, but it can affect an unborn baby. Most babies are fine. Here is how it spreads, how to lower your chances of catching it and what to ask your midwife.

What is CMV?

The NHS says cytomegalovirus (CMV) is a common virus that’s usually harmless. It can cause problems in unborn babies and in people with a weakened immune system. Tommy’s says most people have it, and once you have it, it stays in your body. You can catch it for the first time in pregnancy, it can reactivate, or you can be infected with a different strain.

How it spreads

The NHS says CMV mainly spreads through close contact with someone who has it. It can pass on through saliva, urine, faeces, blood, breast milk and sex. Pregnant women who work closely with young children or have young children at home are at higher risk, because young children often have the virus in their saliva and urine.

Symptoms

CMV does not usually cause symptoms, and most people don’t know they have it. Some people have flu-like symptoms the first time, such as a high temperature, aching muscles, tiredness, a rash, nausea, a sore throat and swollen glands. These usually clear up in about 3 weeks. See your GP if you have symptoms and you’re pregnant, as they may arrange tests.

How it can affect your baby

CMV that is passed to a baby during pregnancy is called congenital CMV. Tommy’s says about 3 to 5 in 1,000 babies are born with it. The UK National Screening Committee puts it at about 1 in 200 babies, and says about 1 in 5 of those may have long-term problems, including hearing loss that can show up later. Most babies with congenital CMV have no symptoms. About 1 in 10 have problems at birth, and about half of those have lifelong problems, most often hearing loss.

Tommy’s says the risk of harm to the baby is highest if you catch CMV for the first time in early pregnancy (the first 12 weeks), and seems to be very low after that, although CMV can still pass to a baby later in pregnancy, so tell your midwife if you have symptoms. Possible signs in a baby at birth include jaundice, a rash, an enlarged liver or spleen, a small head, fits, deafness and low birth weight. The NHS says babies with congenital CMV may have tests of their kidneys, liver, brain, eyes and hearing, with regular follow-up.

Some children who had no symptoms at birth go on to have hearing, learning or communication difficulties, which is why follow-up matters.

How to lower your chances of catching it

There is no vaccine. The NHS and Tommy’s suggest:

Wash your hands with soap and water, especially after changing nappies, feeding young children or wiping their noses.
Wash toys and other items that may have a child’s saliva or urine on them.
Don’t share food, cutlery or drinking glasses with a young child.
Don’t put a child’s dummy in your mouth.
Avoid kissing young children on the mouth.

These are habits to try, not rules to feel guilty about. They lower the chance of catching CMV but can’t remove it, and many people with young children catch it anyway.

Testing and screening

Tommy’s and the UK National Screening Committee say routine CMV screening is not currently recommended, either in pregnancy or for newborns. In 2026 the committee decided against newborn screening and asked for more work on antenatal screening. Testing is usually offered if you have flu-like symptoms, glandular fever or hepatitis in pregnancy, or if a scan suggests your baby may be affected. If you’re worried, speak to your midwife or GP about your own situation, for example if you work with children.

If you test positive

The NHS says that in most cases CMV doesn’t cause problems. Tommy’s says that if you catch CMV for the first time in the first 12 weeks, taking an antiviral medicine called valacyclovir reduces the risk of your baby getting infected, so ask your doctor whether it might be an option for you. The NHS says there is currently no routine treatment for CMV in pregnancy. If CMV is confirmed, you may be offered extra scans, including an MRI of your baby’s brain at 28 to 32 weeks.

If your baby is diagnosed after birth, Tommy’s says they should be tested by 21 days old, using a urine or saliva sample. The NHS says antiviral medicine can be given to babies with symptoms. It does not cure the infection but lowers the risk of serious problems, and Tommy’s adds that it can help prevent hearing loss. A newborn hearing test is offered to every baby. If your baby had CMV, ask about extra hearing checks, because hearing loss from CMV can appear later even after a pass. The NHS says babies with congenital CMV are followed up regularly until around age 5. See newborn checks and the hearing test.

You can call the Tommy’s midwives free on 0800 014 7800 (Monday to Friday, 9am to 5pm).

Questions people ask

Should I be worried if I work with young children?

You’re at higher risk of catching CMV, but most babies are not affected. Follow the hygiene steps, tell your midwife about your job and ask for advice that fits your workplace.

Will my baby be born with CMV if I get it in pregnancy?

Not necessarily. CMV doesn’t always pass to the baby, and most babies who are infected have no symptoms. Across the UK about 1 in 200 babies are born with CMV (UK National Screening Committee). The risk of serious harm is highest if you catch CMV for the first time in the first 12 weeks.

Can I get a CMV test just to check?

Routine screening isn’t recommended in the UK, so a test is not usually offered unless you have symptoms or a scan raises a concern. Talk to your GP or midwife if you’re worried.

Does having had CMV before protect me?

Not completely. Tommy’s says you can be infected with a new strain, or the virus can reactivate. The risk of harm to a baby is generally highest with a first infection in early pregnancy.

Is CMV the same as chickenpox or toxoplasmosis?

No. CMV is a different virus and a different risk. See chickenpox, shingles and other infections in pregnancy for others.