Congenital cytomegalovirus CMV infection affects about 0.2-2.5% of babies worldwide.
Your baby's risk of becoming infected with CMV cytomegalovirus depends on whether you had it already before pregnancy or not. Whether you have already developed antibodies or not before you become pregnant. In addition, the severity of symptoms of the infection is depended on whether you become infected for the first time during pregnancy as well as when during pregnancy the infection first happened.
First-time infection during pregnancy
A first time or primary infection is when you become first infected during pregnancy. When you had no antibodies and then become infected. The transmission rate to the fetus with a primary CMV infection is between 30-50%. Only 10-15% of those infected show signs of congenital CMV after a primary maternal infection.
Recurrent infection
A recurrent infection is when you infect the fetus during pregnancy but you had previously already become infected and you already have antibodies to CMV. For a woman who has a recurrent CMV infection during pregnancy (meaning this is not a primary infection), the rate of newborn CMV infection is about 1%. Of these, only 1-10% of the babies born with the CMV infection will have symptoms at birth and another 10-15% may not show any symptoms at birth, but still may have long term effects such as hearing loss and learning disabilities.