CMV infection during pregnancy can lead to intrauter- ine fetal infection and congenital CMV disease. Con- genital CMV infection occurs most commonly among infants born to mothers who developed primary CMV infection during pregnancy. In this situation, transmis- sion of infection has been described to occur in ap- proximately 40% of cases ( 35). The risk of transmission is highest if CMV infection occurs during the first half of pregnancy, although it may occur at any stage. Less commonly, transmission of CMV may occur among infants born to CMV-immune women, when the mother is superinfected with a different strain of CMV, since preconceptional immunity provides only partial protec- tion