Intrauterine or congenital CMV infections occur in 0.5 to 2.2% of all live births. Symptomatic congenital infections usually occur in infants born to nonimmune mothers who have primary infections duing pregnancy. Latency and reactivation of CMV influence the interpretation of serological results. A single positive CMV influence the interpretation of serological results. A single positive CMV IgG result is an indication of present or past infection. The presence of CMV IgM suggests a recent CMV exposure but does not differentiate between primary infection and reactivation.