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The incidence of congenital CMV is 0.3% - 0.4% in the U.K. Approximately 30 to 50% of these cases are due to a reactivation of the virus (1)

About 1% of all seropositive mothers transmit the infection to the fetus (1)

A review states that:

  • congenital cytomegalovirus (cCMV) is common, occurring in one in every 100-200 live births globally (2)

Primary versus non-primary CMV infection (2)

  • 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


  • Paryani et al (1985), Journal of Pediatrics, 107, 451
  • Pesch MH et al. Congenital cytomegalovirus infection.BMJ 2021;373:n1212 | doi: 10.1136/bmj.n1212.

Last edited 06/2021 and last reviewed 06/2021