Cytomegalovirus (CMV) in Pregnancy


What is CMV?

Cytomegalovirus (CMV) is a common herpes-like virus.  It is thought that up to 85% of the population contract CMV in some stage of their lives by the time they reach 40 years of age.  Peaks of infection occur in children less than two years of age and during adolescence.  Once a person becomes infected, the virus remains alive but usually inactive (dormant) within that person’s body for life.  It is unusual for a person to display symptoms after the initial infection unless their immune system is weakened by severe illness.

What are the symptoms of CMV?

Children and adults with healthy immune systems do not usually develop significant symptoms when infected, but may develop an illness similar to glandular fever with tiredness, sore throat, swollen glands and mild fever.  People with a weakened immune system are those most likely to develop symptoms.

How is CMV spread?

Humans are the only source of CMV.  The virus is found in urine, saliva, nasal mucus, breast milk, vaginal secretions and semen of infected people.  CMV is spread through:

  • Close contact with a person excreting the virus in their saliva, nasal mucosa, urine or other body fluids
  • Handling children’s toys that have saliva or mucus on them, or handling contaminated items such as dirty tissues or soiled nappies and then touching the eyes, nose and mouth without washing hands first
  • From mother to her unborn child as a result of maternal infection during pregnancy
  • From mother to her unborn child as a result of virus reactivation during pregnancy
  • Breast milk of an infected woman who is breast feeding.
  • Sexual contact

Who is at risk?

If a woman is newly infected with CMV while pregnant there is a risk that her unborn baby will also become infected (congenital CMV).  Infected babies may, but not always, be born with a disability.  The highest risk to the unborn baby occurs when a woman who has never had CMV before is infected with the virus for the first time during pregnancy (primary CMV infection), and when infection occurs during the first 20 weeks of the pregnancy.  Studies in Australia have shown that out of 1000 live births approximately six infants will have congenital CMV infection and one to two of those six infants (about 1:1000 infants overall) will have permanent disabilities of varying degrees.  These can include hearing loss, vision loss, small head size, cerebral palsy, developmental delays or intellectual disabilities.  In the most extreme cases the virus can cause stillbirth, neonatal death and the severe condition cytomegalic inclusion disease (CID).

How can congenital CMV be prevented?

There is currently no vaccine against CMV although research is under way to formulate a CMV vaccine.  Pregnant woman are recommended to take steps to reduce their risk of exposure to CMV and so reduce the risk of their developing baby becoming infected.  Preventive steps include:

  • Wash hands often with soap and running water for at least 15 seconds and dry them thoroughly. This should be done especially after close contact with young children, changing nappies, blowing noses, feeding a young child, and handling children’s toys, dummies/soothers
  • Do not share food, drinks, eating utensils or toothbrushes with young children
  • Avoid contact with saliva when kissing a child
  • Use simple detergent and water to clean toys, benchtops and other surfaces that come into contact with children’s urine, mucus or saliva

How is congenital CMV diagnosed?

The person who has been infected with CMV will develop antibodies in their blood that indicate infection has occurred either recently or in the past.  These antibodies stay in the body for the rest of that person’s life.  Other tests that detect the virus are used to determine if a person has an active CMV infection.  Testing for CMV is not routinely recommended for all women during pregnancy or for newborn babies.  CMV testing is currently recommended for pregnant women who develop an acute viral illness or when an ultrasound reveals a fetal abnormality.  Pregnant women and those women planning a pregnancy should discuss CMV testing with their doctor, particularly if they work in high-risk settings, such as child-care centres, or have very young children at home.  Infants born to mothers diagnosed with primary CMV infection during pregnancy should be tested for congenital CMV infection.  Babies who do not have a normal hearing screening test at birth can also be tested for congenital CMV as hearing loss is the most common sign of congenital CMV.  However, some infants with congenital CMV infection who appear healthy at birth develop hearing or vision loss over time.  For this reason babies known to be infected should have their hearing and vision assessed regularly.

The Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) have recently initiated recommendations to increase the awareness of CMV.

Dr Len Kliman is one of Melbourne’s most experienced and trusted obstetricians and gynaecologists.

With over three decades of experience, Dr Kliman has delivered over 20,000 babies and still counting. He has treated tens of thousands of gynaecological patients.

In 2017, Dr Kliman was awarded an Order of Australia for his services to obstetrics and gynaecology.