Primary CMV infection in the mother can be diagnosed by documenting positive serology in a woman previ- ously known to be seronegative. CMV-specific IgM can be detected in women with primary infection; however, they may persist for 6 to 9 months after infection ( 38, 170). IgG-avidity assays can be utilized to distinguish primary from reactivation infections. A combination of CMV-IgM with IgG-avidity assays increases sensitivity for detecting a mother who could potentially transmit CMV to her offspring ( 171). The use of QNAT or pp65 antigenemia for diagnosis of primary maternal CMV infection is limited, since less than 50% of pregnant women have detectable viral replication