CMV is a common virus that infects people of all ages. Most CMV infections are "silent," meaning the majority of people who are infected with CMV have no signs or symptoms, and there are no harmful effects.
However, when CMV infections occurs during a woman's pregnancy, the baby can become infected before birth. CMV infection of the baby before it's born is called congenital CMV, or cCMV. When this happens, the virus can get transmitted to the unborn baby and can potentially damage the baby's brain, eyes, and hearing.
About 1 out of every 5 babies born with cCMV will develop permanent problems, such as hearing loss or developmental disabilities.