Cytomegalovirus (CMV) in pregnancy

What is it?

CMV is a common infection which is a member of the herpes virus family.

Most healthy children and adults infected with CMV have no symptoms and may not even know that they have been infected. Others may develop a mild illness; symptoms may include fever, sore throat, rash and fatigue.


How is CMV spread?

CMV is mainly spread through close contact with someone who already has CMV. It can be passed on through bodily fluids including saliva, blood and urine.

CMV can also be transmitted to the unborn baby through the placenta and this is called congenital CMV. There are particular concerns when this type of infection occurs:

  • Most cases of CMV develop for the first time during or shortly before pregnancy
  • In some cases, an old CMV infection can become active in pregnancy because of the weakened immune system
  • Even if you have had CMV before you can still become re-infected with a different strain of CMV (although the risk is very low).

How this affects the baby

If you have contracted CMV this does not mean that your baby has the virus.

If this is a first time (primary) CMV infection, then just over a third of all women will pass it to their baby. It is important to remember that around 4 out of 5 babies born with CMV do not have any health problems.

A small number of babies may be born with birth defects such as poor hearing, visual problems or intellectual impairment. This seems more likely in mothers who have a first time (primary) infection.

If this is a not a new infection, then the risk of problems to baby are much lower.

What happens next?

CMV infection is normally diagnosed by a blood test (occasionally can be suspected after a scan). This blood test will be compared to the early booking blood taken at 12 weeks of pregnancy which is already stored in the laboratory. The comparison of blood is to try to ascertain whether it is a new or old infection.

Initially you can discuss the results of your blood test or scan with the Fetal Medicine Midwife or appropriately trained professional.

A referral to Fetal Medicine Clinic will be made and during this appointment you will have a further scan and be able to discuss your plan of care in more detail with the Consultant Obstetrician.


Additional scans will be arranged to assess baby’s wellbeing and growth.

Further tests such as amniocentesis will be discussed in Fetal Medicine Clinic.

(click here for Antenatal Screening Wales for information on procedure)

You will have an anomaly scan at 19 weeks pregnant with the senior sonographer.

During pregnancy you will be referred to the Neonatologist (Doctor who cares for new-born babies). You will have an opportunity to discuss the plan for baby after delivery.


It is desirable to have a normal vaginal delivery at full term unless any contraindications. This will be discussed later in pregnancy with your Consultant Obstetrician.

Care of Baby

When baby is born a full examination by the neonatologist will be performed.

A urine sample from baby will be collected to confirm whether the CMV virus is actually present.

If the urine result shows that the CMV virus is not detected and baby is well then, no further treatment or follow up is necessary.

If the CMV virus is detected in the urine, then further investigations and regular Paediatric follow up will be arranged prior to discharge.

Anti-viral medication for baby may be recommended. The goal of anti-viral treatment is to reduce the amount of active virus so that baby is able to control the infection with his or her own immune system.


We understand this is an uncertain and stressful time for you. If you have any questions or concerns, please contact the Fetal Medicine Midwife on:

Contact Numbers

Royal Gwent Hospital 01633 234747

Nevill Hall Hospital 01873 732390 or 01873 732391

Useful Websites

ARC (Antenatal Results and Choices) - Offer information and support to parents who are making decisions before, during and after tests in pregnancy

Tel no: 084507722990


Email: info@arc-uk-org

ASW (Antenatal Screening Wales)


CMV Action –


Helpline Tel no 0808 802 0030


Improving the physical and emotional health and wellbeing of expectant mothers, infants, children and young people throughout Aneurin Bevan University Health Board Area.

(N.B: The Family and Therapies team at ABUHB is NOT responsible for the content on the webpage links that we refer to in our resource sections and linked information to external sites. All information was accurate and appropriate at the time the webpage was created.)

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