Human Cytomegalovirus are speherical approximately 120-200 nm in diameter, The virus is considered as the largest member of the herpesviruses family and it's genome is the largest genome of all herpesviruses so the number of the virus encoded proteins and complexity of their functions in the life cycle of the virus reflect the size of its genome . The virus has a double stranded linear DNA genome approximately 230-240 kb in size . Human Cytomegalovirus can be transmitted from the mother to the fetus trancplacently during pregnancy in about 40% of cases ,then HCMV can impairs Cytotrophoblasts differentiation a matter that may explain early abortion occurring in women with primary infection .