cytomegalovirus (foetal infection)

Last edited 11/2021 and last reviewed 11/2021

Antibodies to cytomegalovirus (CMV) are found in about 50% of pregnant mothers in the UK. Between 1 and 6% of women become infected with CMV during pregnancy and about 40% of the foetuses are affected. Foetal infection may occur when the mother is asymptomatic.

At present there are no reliable CMV vaccine available. Prevention is best achieved by reducing women's exposure to toddler's urine (which is often the source of infection). Equally, blood for donation to infants should be from CMV-negative donors.

Treatment is generally supportive

• treatment with a six month course of valganciclovir starting in the first month of life has been associated with improved hearing and developmental outcomes at 24 months (3)

Note also that reactivation of CMV infection may occur - if this occurs during pregnancy it is rare for fetal infection to occur.

The UK National Screening Committee have stated that available evidence does not support routine cytomegalovirus screening in pregnant women and it should not be offered (1).

However a study involving vaccination CMV-seronegative women revealed that CMV glycoprotein B vaccine has the potential to decrease incident cases of maternal and congenital CMV infection (2).

A review suggests (3):

• congenital cytomegalovirus (cCMV) is common, occurring in one in every 100-200 live births globally
  
  
• the mainstay of prevention is prenatal education about behaviour change to reduce contact with saliva and urine of young children who may be shedding
  CMV
  
  
• cCMV most often presents with no visible signs at birth, yet infected infants are at increased risk for sensorineural hearing loss in childhood
  
  
• cCMV can be diagnosed shortly after birth using polymerase chain reaction to detect viral DNA in urine or saliva, or later in life by testing residual newborn
  dried blood spot (Guthrie card)
  
  
• All children with cCMV require close monitoring of their hearing and development

Cytomegalovirus (CMV) can cause self-limited generalised symptoms such as fatigue and lymphadenopathy in most healthy individuals, including pregnant people

• cCMV infection occurs when CMV transplacentally infects a developing fetus
  • the virus can cause damage to the placenta, and replicate in fetal central nervous system (CNS) cells, which may result in disrupted fetal development, miscarriage, or intrauterine fetal demise
  • neonates born with visible signs or CNS involvement, commonly referred to as symptomatic, make up 10% of cCMV cases and are at increased risk for long term neurodevelopmental sequelae
  • neonates born without visible signs of infection or CNS involvement, referred to as asymptomatic, make up 90% of cases
    • approximately 15% of asymptomatic neonates develop isolated sensorineural hearing loss (SNHL), which may progress

Treatment (4):

• treatments licensed for CMV disease in children are:
  • ganciclovir, valaciclovir and valganciclovir
  • ganciclovir can be used for the prevention of CMV diseases, however, it is not licensed in neonates for cCMV infection of the CNS
• is still no established treatment for CMV in asymptomatic newborns, or during pregnancy

Primary versus non-primary CMV infection

• primary infections
  • occur when CMV is contracted for the first time just before or during pregnancy, posing a 30-35% risk of fetal transmission
• non-primary infections
  • occur when the childbearing parent has pre-existing CMV immunity but is exposed to a different strain, or has a reactivation of a latent infection
  • risk for fetal transmission is lower (approximately 1%) with non-primary infections
• primary infections (versus non-primary) and those that occur earlier (versus later) in gestation are associated with poorer fetal outcomes

• advice from the UK National Screening Committee on antenatal screening for cytomegalovirus..click here

Reference:

1. UK National Screening Committee. Antenal Screening Programme - Cytomegalovirus (Accessed 15th November 2021)
2. Pass RF et al. Vaccine prevention of maternal cytomegalovirus infection. N Engl J Med. 2009 Mar 19;360(12):1191-9.
3. Pesch MH et al. Congenital cytomegalovirus infection.BMJ 2021;373:n1212 | doi: 10.1136/bmj.n1212
4. Rawlinson WD, Hamilton ST, van Zuylen WJ. Update on treatment of cytomegalovirus infection in pregnancy and of the newborn with congenital cytomegalovirus. Current opinion in infectious diseases 2016;29:615-624