How to avoid a Cytomegalovirus (CMV) infection during pregnancy

And here’s a very important update from May 2024 – new national guidelines were published in my countryy about prevention, investigations and treatment of CMV infection during pregnancy. The guidelines, and mainly the screening aspect of them, are summarized here.
But this chapter about prevention is as relevant as it has ever been, and it is thoroughly summarized below.

Before we begin, it is important to learn to distinguish between a primary maternal infection and a non-primary (or secondary) infection – lets go over what these definitions mean.

What is a primary infection and what is a non-primary CMV infection in pregnancy?

According to several epidemiologic studies in my country, about 80% of fertile women have already had a CMV infection in the past. Some of them remember having it and others do not. You can find out whether you have had the infection with the help of serological tests (antibody testing in the blood). This can be done in the beginning of the pregnancy.
This means that about 20% of women will begin their pregnancy not having had a previous CMV infection (without medical history of a previous infection).
Primary CMV infection in pregnancy – a woman that has not had the infection in the past and gets the infection for the first time during pregnancy. Since she does not have any antibodies, the infection can pass the placenta and expose the fetus to the risk of infection, especially if it occurs during the first few months of pregnancy.
Non-primary CMV infection in pregnancy – a woman who has antibodies (has had the CMV infection prior to the pregnancy) but the virus reactivated during the pregnancy and infects her again, or a woman who previously experienced a different type of CMV. In these situations, the virus can still be transmitted to the fetus but the risk of harm to the fetus is much lower than in the primary infection.

Are we able to avoid a CMV infection in pregnancy? How so?

It is well known that most CMV infections occur as a result of a pregnant woman being exposed to children at home, especially if they are in daycare. Keep in mind that children that carry the virus may not always show overt symptoms but do secrete large quantities of the virus in urine and saliva.
An important Italian paper that was published several years ago demonstrated that one can prevent primary CMV infections by following several rules. These were further summarized in the recent national guidelines:
1. An explanation on how CMV is transmitted – it is important to teach pregnant women about this infection and that it is transmitted mostly through bodily secretions such as saliva.
2. Washing hands with water and soap after exposure to children’s secretions (saliva, cleaning their nose, changing diapers, etc.). Some would also say washing hands after touching surfaces that were touched by children (toys, chairs, etc.).
3. Avoidance of kissing children under the age of 6 in the areas of the mouth, cheeks or forehead.
4. Avoidance of placing children’s soothers in the parent’s mouth.
5. Avoidance of sharing eating or drinking utensils with children

And to all those who think these steps are too drastic, you do not want to experience the stress and anxiety of a pregnancy with CMV, even if the results are mostly good and the fetus does not get the infection and does not get sick.

Is a non-primary CMV infection in pregnancy preventable?

As I mentioned above, a non-primary CMV infection can happen through one of two mechanisms:
A reactivation of the latent primary virus in the mother – this cannot be prevented.
A new CMV infection – there is no evidence for this in the scientific literature but it is probably reasonable to think that the five rules described above would prevent this type of infection.

How can we detect a primary CMV infection in pregnancy?

You will have to read about this in our chapter about screening pregnant women for CMV.

What if an infection does occur during pregnancy?

I strongly recommend going to the website about CMV infections under The Israeli Association for CMV pregnancy. This is a website that was written through the tears and blood of amazing women who experienced CMV in pregnancy.
My website also has a summary of the original paper that demonstrated the efficacy of Valacyclovir in women who experienced the infection early on in their pregnancy.
But remember, prevention of the disease is better than treatment. Follow the 5 rules mentioned above so that together we can help reduce the prevalence of congenital CMV infections.

And if you are at the start of your pregnancy, remember that there is another infection that we want to try and prevent and that is toxoplasma.
I wish you all lots of health.