In the case of unknown serological status of the patient before pregnancy, the diagnosis of primary hCMV infection is made on the basis of the detection of hCMV-specific IgG with medium or low avidity, as well as hCMV-specific immunoglobulins in class M (IgM) in the blood serum [40,41,42,43]. This evidence concerns the gene CD40LG and cytomegalovirus infection.