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 [first] CMV infection) and when infection occurs during the first half of the pregnancy.
Studies in Australia have shown that out of 1,000 live births, about 6 infants will have congenital CMV infection and 1-2 of those 6 infants (about 1 in 1000 infants overall) will have permanent disabilities of varying degree. These can include hearing loss, vision loss, small head size, cerebral palsy, developmental delay or intellectual disability, and in rare cases, death. Sometimes, the virus may reactivate while a woman is pregnant but reactivation does not usually cause problems to the woman or her unborn baby.