What is the meaning of "cmv IgG was 12"?

CMV. A positive or elevated CMV igg simply means prior exposure, infection or immunization with a CMV viral infection.
Prior Exposure. All labs have varying cut-off values, but it may signify that you have been exposed to CMV infection in the past. It is a very common virus. If you are pregnant, the key to figuring out whether your pregnancy may be at risk is CMV antibody avidity testing. Ask you maternal fetal medicine specialist or ob/gyn about getting this test.