Cytomegalovirus and pregnancy: risks, tests and prevention

There are some pathologies which, if contracted under normal conditions, have no consequences. However, if infections such as  toxoplasmosis , rubella or cytomegalovirus (CMV), just to name a few, are contracted during pregnancy, in some cases the consequences can be relevant and serious.

Cytomegalovirus (CMV) belongs to the herpesvirus family. The infection is usually asymptomatic. In immunosuppressed people, however, it can cause some complications in the eyes, liver, gastrointestinal system and nervous system.

It is contracted mainly in childhood or adolescence but also in adulthood. As adults, problems can arise if this virus is contracted during pregnancy as, transmitted to the fetus, it can in some cases cause permanent damage to the child.

Cytolmegalovirus infections in pregnancy

Cytomegalovirus infections acquired during pregnancy are classified into two types: primary and secondary.

Primary in case the expectant mother contracts the infection for the first time during pregnancy; secondary when the infection occurs by reactivation of the latent virus or by new infection with a new strain in a woman who had already contracted the infection.

It is not yet known which gestational period is most at risk, although it seems that the consequences could be more serious if the infection is contracted during the first trimester [1].

What consequences?

If the contagion occurs during pregnancy, in about 4% of cases the newborn will show signs of the disease at the time of birth with sensorineural consequences in the following years, and in a further 4% of cases the newborn will present problems in the first months of life, especially hearing [2]. They are very low numbers fortunately but in these few cases the consequences can be very serious.

Symptoms of the disease can be temporary or permanent: Temporary symptoms include problems with the liver, spleen, lungs, jaundice, petechiae (red patches on the skin due to small bleeding on the skin), small birth size, and seizures.

The permanent symptoms, on the other hand, translate into deafness, blindness, mental retardation, small head size, lack of coordination of movements, convulsions up to death. In some children, symptoms appear months or years after birth, and in these cases the most common are loss of hearing and vision. Permanent disabilities are more likely in children who show symptoms from birth [1]

IgG and IgM values ​​against Cytomegalovirus

Among the preconception tests it would be important that the antibodies for the Cytomegalovirus were dosed. If a woman has been exposed to a recent CMV infection, it would be recommended to wait for her IgM antibody levels to drop to an undetectable level and for her IgG Avidity Index to reach a favorable rate before attempting to conceive.

The waiting time can range from six to twelve months .  Why wait so long? It is important to wait until the CMV infection has resolved in order to minimize the risk of transmission from the pregnant woman to her unborn child.

When you go for tests to check the levels of antibodies for Cytomegalovirus you can get the following results

Results	Interpretation
IgM negativeIgG negative	No previous cytomegalovirus infectionAt risk of primary infection, it is important to take precautions to avoid contagion.
IgM positiveIgG positive	Recent cytomegalovirus infection
IgM negativeIgG positive	Not recent cytomegalovirus infection

Cases that need to be investigated carefully are when IgG and IgM are positive.

A positive cytomegalovirus IgG test indicates that the person was infected with CMV at some point in their life, but does not indicate when a person was infected. (This applies to people older than 12 months when maternal antibodies are no longer present in the baby’s bloodstream).

The presence of CMV IgM alone cannot be used to diagnose primary CMV infection because IgM can also be present during secondary CMV infection.

To trace the period of infection, the avidity test is required.

Cytomegalovirus avidity test

Avidity tests are used to understand the timing of Cytomegalovirus infection and are performed when positive IgM and IgG values ​​are obtained.

The primary infection is recent if you have positive IgM results in combination with low avidity IgG results (low avidity = low binding strength)

Two to four months after infection, IgG antibodies mature to high avidity (high binding strength).

Therefore:

• low IgG avidity indicates recent infection
• high IgG avidity indicates previous infection

Obviously the avidity test must be a test with good sensitivity. Not all tests are created equal.

Ultrasound signs of cytomegalovirus infection

A pregnant woman may be advised to have her IgG and cytomegalovirus IgG levels checked when ultrasound detects abnormalities that could be caused by CMV or another infectious disease.

If one or more of the following signs are found during an ultrasound, an amniocentesis should be performed to confirm a congenital CMV infection:

• Placental thickening
• Organomegaly: Abnormal enlargement of organs
• Hepatomegaly: Abnormal enlargement of the liver
• Splenomegaly – abnormal enlargement of the spleen
• Dilatation of the renal pelvis
• Dilatation of the ureter
• Ascites: gastroenterological term to indicate an accumulation of fluid in the peritoneal cavity (it is a potential space between the parietal peritoneum and the visceral peritoneum, i.e. the two membranes that separate the organs in the abdominal cavity from the abdominal wall)
• Fetal hydrops: accumulation of fluid in the fetal compartments
• Amniotic fluid abnormality
• Microcephaly – small head circumference, more than two standard deviations below the mean
• Cerebral ventriculomegaly – dilatation of the lateral ventricles of the brain
• Intracranial calcifications – the accumulation of calcium salts in the soft tissues of the brain
• Hyperdense image in the thalamic arteries
• Periventricular density echo
• Liver echodensities
• Intestinal echo density
• Cystic structures in the germinal zone

If a pregnant woman is diagnosed with CMV infection during pregnancy, an amniocentesis is done to determine if the infection has passed to the unborn child. The analysis of the amniotic fluid will in fact also look for the presence of CMV DNA.

 How to prevent contagion?

The cytomegalovirus could clearly frighten reading the consequences of an infection. The important thing is to do a simple blood test before deciding to have a baby

This examination  should be prescribed before each pregnancy  ( http://www.pensiamociprima.net/ ) in order to know if we have to adopt some particular hygiene rules during pregnancy or if we can rest assured because we have already caught the infection in the past .

Those who work in contact with children could be at risk of infection, as it is a very common virus in childhood and is transmitted through saliva, tears, pee … and all those objects that have come into contact with these organic liquids . Surely kindergartens are a good source of infection.

If the preconception exam shows that we have never contracted the virus, these are the rules to follow [2]:

• wash your hands very well  with soap and water especially if you are in contact with small children (under 3-5 years old)
• do not share crockery, cutlery, toothbrushes, etc. with small children
• keep children’s toys clean

 Testing for CMV virus during pregnancy is not currently recommended . This is mainly because there are no effective treatments, it is not possible to know a priori any damage to the fetus and because the mother would live in an excessively anxious state during pregnancy.