Cytomegalovirus (CMV) in pregnancy: risks, testing, prevention

What is cytomegalovirus?

Cytomegalovirus is a very common virus from the herpes family. It spreads through saliva, urine, tears and genital secretions. Young children, especially those at nursery, often shed it for months without being ill: they are the main source of infection for pregnant women.

After a first infection, the virus stays dormant in the body for life, like the cold sore virus. Some women have therefore already met the virus before pregnancy; others can have a primary infection during pregnancy. This infection is one of the topics discussed at the start of pregnancy care, described on our page Giving birth in Paris.

According to the 2024 European ECCI consensus, about 0.64% of newborns worldwide are infected at birth, and 17 to 20% of them will have lasting effects. In France, according to the HAS, about 0.4% of newborns are infected; it is the leading infectious cause of congenital disability.

What are the symptoms of CMV in pregnancy?

In the vast majority of cases, the infection goes completely unnoticed. Sometimes it causes flu-like symptoms: tiredness, a prolonged mild fever, aches, headaches, swollen glands. A blood test may show mild liver involvement.

These signs are not enough for a diagnosis. Diagnosis relies on blood tests: the appearance of IgG antibodies in a woman who did not have them before (seroconversion), or IgM together with low-avidity IgG, which points to a recent infection. A fever during pregnancy always needs medical advice; see fever during pregnancy.

What is the risk of CMV to the baby?

In a primary infection in the mother, the virus crosses the placenta in about 30 to 40% of cases. The risk of transmission increases as pregnancy goes on, but severity depends mainly on when the infection occurs: long-term effects mostly concern infections in the two months before conception or in the first trimester; after 14 weeks, the risk of long-term effects is almost nil according to the HAS.

A reinfection or reactivation in a woman who is already immune can also pass the virus on, but severe forms are much rarer.

Should I have a CMV blood test in pregnancy?

Yes. On 17 June 2025, the HAS recommended universal screening for CMV in all pregnant women whose status is unknown or negative, for an initial 3 years followed by reassessment. The details were set out on 4 August 2026:

• if you are planning a pregnancy, the blood test (IgG and IgM) is done before conceiving, including during fertility treatment;
• if it is negative, it is repeated as soon as you are pregnant and then every 4 weeks during the first trimester, the last one between 13+0 and 14+0 weeks;
• if it was not done before pregnancy, it should be done as early as possible and before 14 weeks; after 14 weeks, screening is no longer useful;
• a woman who is already immune (IgG positive, IgM negative) needs no particular monitoring;
• if a recent infection is found before pregnancy, pregnancy is postponed by 2 months.

The test is also prescribed if there are suggestive symptoms or when the scan shows signs consistent with infection of the foetus. Discuss it as soon as you plan a pregnancy or at your first pregnancy appointment.

How is CMV infection treated during pregnancy?

• Valaciclovir: a randomised trial published in 2020 showed that an antiviral, high-dose valaciclovir, reduces passage of the virus to the foetus after a primary infection around conception or in the first trimester (positive amniocentesis in 11% of treated women versus 30% with placebo). If a primary infection occurs in the 2 months before pregnancy or in the first trimester, the HAS recommends a dedicated appointment, linked with a prenatal diagnosis centre, and valaciclovir started as early as possible. It is prescribed off-label, under a compassionate-use framework from the ANSM (French medicines agency) that is being drawn up. During treatment, drink plenty of fluids and spread the doses over 24 hours.
• Amniocentesis: testing the amniotic fluid for the virus is offered as soon as possible from 18 weeks according to the HAS. If it is negative, valaciclovir is stopped; if it is positive, care continues with the prenatal diagnosis centre. It shows whether the foetus is infected, but cannot on its own predict severity.
• Frequent scans, sometimes with a foetal brain MRI, to look for damage.
• At birth: testing the baby's saliva or urine for the virus in the first days, a hearing test, and specialist follow-up.

Care is coordinated by a multidisciplinary prenatal diagnosis centre. In the most severe forms, a termination of pregnancy for medical reasons may be discussed with the couple, who remain free to decide.

How can I avoid catching cytomegalovirus while pregnant?

There is no vaccine. The HAS recommends that all women are informed about hygiene measures as soon as a pregnancy is planned, whatever their immune status, because a first infection does not protect against reinfection. These measures mainly concern contact with children under three:

• wash your hands with soap after every nappy change, bath, nose wiping or contact with saliva, toys or dummies;
• do not share the child's cutlery, glass, toothbrush or food, and do not finish their plate;
• do not put their dummy or spoon in your mouth;
• avoid kissing on the mouth and kiss the forehead or hair instead;
• regularly clean toys and surfaces that come into contact with saliva;
• use disposable tissues and throw them away straight after use.

Women working with young children (nurseries, nursery schools, childminders) are more exposed: in France, tell the occupational health doctor about your pregnancy so your duties can be adapted if needed.

When should I go to the maternity unit urgently?

A prolonged fever or flu-like illness during pregnancy needs prompt medical advice, especially in the first trimester.

Some signs should not wait for your next appointment. Go directly to your maternity unit's emergency department (open day and night), the one where you are registered (Maternité Sainte-Félicité or Clinique Sainte-Thérèse), if you have:

• any vaginal bleeding, even light;
• a leak of fluid, clear or coloured, from the vagina;
• regular or painful contractions before 37 weeks;
• fewer or no movements from the baby (once you usually feel them);
• a fever of 38 °C or more, shivering, or burning when passing urine with back pain;
• severe headaches, vision problems, pain under the right ribs or in the pit of the stomach, sudden swelling of the face or hands;
• severe or constant abdominal pain, a fall or a blow to the abdomen;
• intense itching of the palms and soles of the feet, especially at night.

If you feel faint, have heavy bleeding or very severe pain, call 15 (SAMU) or 112 in France, or your local emergency number.

Frequently asked questions

General information article: it does not replace a medical consultation. In an emergency, call 15 or 112 in France, or your local emergency number.