Screening for Cytomegalovirus During Pregnancy

Cytomegalovirus (Cmv) Is A Member Of The Herpes Virus Group And Is Considered An Important Pathogen In Particular When Manifests Itself During Pregnancy. The Maternal-Fetal Infection By Cmv Is The Leading Infectious Cause Of Birth Defects, Psychomotor Retardation And Deafness.

Screening for Cytomegalovirus During Pregnancy

The virus is usually present in bodily fluids such as saliva, urine, blood, milk, feces, vaginal and cefalorraquiano liquid. The newborn can contract the infection at the time of delivery, through the vaginal secretions or by postnatal contact, through breast milk. In the majority of cases, the infected baby remains symptom-free, but theinitial infection can cause serious health problems, with regard to hearing, vision and mental development delay.

The clinical suspicion of maternal Cytomegalovirus infection must be confirmed bylaboratory diagnosis, through methods of ELISA, an enzyme-linked immunosorbent assay allowing detection of IgG and IgM class antibodies, and your sensitivity and specificity very close to 100%. The test is based on research and determination of IgM and IgG class antibodies produced by the body in response to an infectious agent. IgM antibodies are usually the first to be produced in response to an infection and are detected within one to two weeks after the initial exposure to the virus.

These remain for a longer period of time reduced, usually disappear between three to six months after infection, while IgG antibodies prevail for longer periods of time, sometimes for the life of the human being. Thus, the presence of IgM antibodies is indicative of recent infection and the presence of IgG points to the existence of a chronic infection.

If IgM is reactive or negative and reactive or positive IgG is indicative that the woman already had contact with the virus and the risk of transmission is reduced. IGM and IgG reactive or negative not reveal that the woman was never in contact with the virus, soon every precaution must be taken to avoid this contact and if the IgM and IgG antibodies may occur as reactive or positive, the attending physician must request a test of greed, the result of which, if it is less than 30% (low avidity), reveals that there is a high risk of infection of the fetus during pregnancy. The severe infection by CMV is confirmed when laboratory results obtained in reactive or positive IgM and IgG reactive or not negative.

The CMV infection contracted during pregnancy should be treated as soon as possible, in order to prevent infection of the fetus through the placenta or during childbirth. The first organ to be infected is the placenta, where the virus reproduces. The placenta acts as barrier and as a reservoir that can release the virus in fetal circulation.

The obstetric ultrasound is also a method available to assess the well-being of the fetus, constituting a great screening tool impact of fetal infection by CMV. In case of presence of the virus, will be visible on the ultrasound placentar thickness increase associated with a globally diverse aspect, sometimes with calcifications that coexist with hipoecogénicas areas.

By Maria Jose Rego de Sousa, m.d., PhD in Medicine, specialist in clinical pathology


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