Cytomegalovirus (CMV)

CMV is a virus. In children and adults, it may cause symptoms similar to a cold or mild flu. If a developing fetus becomes infected, the problems can be severe (deafness, eye problems and blindness, mental retardation and death).

Cytomegalovirus infection is difficult to diagnose with precision, and very difficult to diagnose in the fetus. Fortunately, in most cases where a mother is infected, the baby is not. It is possible for a good laboratory to grow CMV in a culture from maternal fluid specimens (blood, urine, saliva/throat) and amniotic fluid. Amniotic fluid culture is the primary tool for determining whether or not a fetus has been infected……however, it cannot determine the degree of infection or damage. In pregnancies with positive amniotic fluid cultures, ultrasound must be done repeatedly to determine if there are severe complications with the fetus.

It is possible to look for the antibodies which a person produces in response to CMV. But unlike a disease such as measles, in which most cases a person acquires lifelong immunity after infection, the CMV virus may remain in the body in a dormant state and cause re-infection later. Thus, looking for the presence of IgG antibodies (which with other viruses suggests immunity) is not always helpful. A four-fold increase in the IgG level is considered indication of reactivation of the virus. And, the presence of CMV-specific IgM antibodies is indicative of recent infection.

In most cases a fetus is infected when a mother develops CMV infection for the first time during pregnancy. Women, who have had CMV in the past (those with positive IgG and no evidence of recent infection) may provide some protection for their babies from the maternal IgG antibodies. But reactivation of dormant CMV is a known cause of fetal and neonatal infection.

Even if a mother and fetus are shown to be recently infected, there is little in the way of treatment. Viruses are not like bacteria with regards to our ability to treat with antibiotics. The antiviral drugs which are currently available work with only limited success in eradicating the virus.

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