Seroconversion to cytomegalovirus (CMV) occurs in 1-4% of pregnant women. The majority of these women are seropositive prior to pregnancy. In 0.2-2.5% of the newborn infants, there is evidence of intrauterine infection, most of them are born without any clinical findings. The typical clinical symptoms of congenital CMV (symptomatic congenital CMV) that are found in 10-20% of infected neonates include intrauterine growth restriction (IUGR), microcephaly, hepatosplenomegaly, petechiae, jaundice, chorioretinitis, thrombocytopenia, anemia and/or other atypical findings. Of special problem are the different neurodevelopmental sequelae such as mental retardation, motor impairment, sensorineural hearing loss or visual impairment, which may occur even in infants who are free of symptoms at birth. Most infants born with severe neonatal symptoms of congenital CMV are born to mothers with primary infection in pregnancy. However, since over 60% of the infants infected in utero with CMV are born to mothers with preconceptional immunity who have secondary infection in pregnancy, and more and more studies show severe sequelae in these infants, we have to conclude that congenital CMV may be a significant problem even in children born to mothers with pre-pregnancy immunization. This may justify the use of invasive methods for the detection of possible fetal infection even in cases of secondary CMV infection. This also brings in an additional problem, when considering the need for proper immunization against CMV, as immunization is primarily aimed for women without immunity.