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CMV In Pregnancy: What Should I Know?

CMV Cytomegalovirus (CMV) is the most common virus most people have never heard of! It is the most common congenitally acquired virus, and about 1 out of every 100 to 150 newborns is born congenitally infected with CMV. It is common in both children and adults. Between 50 to 80 percent of women of childbearing age have caught CMV and between 1 and 5 percent of pregnant women will catch CMV for the first time during their pregnancy. Most CMV infections are "silent" and harmless, but in pregnant women, CMV can be transmitted to the fetus, with sometimes devastating effects to the unborn baby and newborn. Therefore, it is important if you are pregnant, or know someone who is pregnant, to be "CMV Aware" and "CMV Cautious". Women who are pregnant should discuss CMV with their obstetrician. Testing for CMV infection is a simple blood test. And, there are interventions available to help. Unfortunately, studies have shown most women of childbearing age and surprisingly, many obstetricians, are not aware of the most recent advances in management of CMV infection in pregnancy. Because many of the questions I received from my first blog post were about CMV infection during pregnancy, I decided to post some basic information that I hope you find helpful:

What are the signs and symptoms of CMV during pregnancy?

Most CMV infections in pregnant women are "silent" and cause no symptoms.  When symptoms do occur, they most commonly are fever, sore throat, swollen lymph glands and extreme fatigue. Rarely, a rash, cough or diarrhea may occur. These symptoms are not specific for CMV infection and may be cause by other conditions. And, unfortunately, often the first time a pregnant woman is aware of CMV is when she has a baby who is diagnosed with congenital CMV infection. Therefore, blood tests are needed to accurately diagnose a CMV infection during pregnancy.

Is CMV infection common in pregnancy?

Approximately 1-4% of all pregnant women will experience a primary CMV infection during their pregnancy. If you work in a child care setting, the risk increases to approximately 10%. If you have a toddler at home who is actively infected with CMV and shedding CMV in their saliva or urine, the risk is even higher, approaching 50% in some studies.

What is the risk to my baby if I have a CMV infection during pregnancy?

CMV infections in pregnancy may be primary (first infection with CMV) or recurrent (infection with a second strain of CMV or reactivation of your own CMV strain). Approximately 40% of women who experience a primary CMV infection during pregnancy will transmit the CMV infection to their baby, and approximately 60% will not. The reason why some women transmit CMV to their baby and some women do not is not known. Most babies born congenitally infected with CMV will appear normal at birth. However, approximately 10% of babies born congenitally infected as a result of their mother's primary CMV infection during pregnancy will have symptoms in the womb or at birth. Newborns with symptomatic congenital CMV disease at birth may have a variety of signs and symptoms in many organ systems, and also may experience disabilities long term in hearing, vision, cognition and motor development. In some babies with severe congenital CMV disease, the congenital CMV infection is fatal. Therefore a maternal primary CMV infection may carry a significant risk to the unborn baby. Women who experience a recurrent CMV infection also may transmit CMV to their baby, but the occurrence is much, much lower ( 0.1% or less) than after a primary CMV infection (40%), and serious symptoms rarely occur in the fetus or newborn born congenitally infected as a result of a maternal recurrent infection.

How do you test for CMV during pregnancy?

Testing for CMV infection is a simple blood test, called a CMV IgG antibody. It will determine if a pregnant woman has had CMV.  A positive result indicates a current or past CMV infection. A second blood test, called CMV IgM antibody will help determine if the CMV infection is current or past. If positive, the infection may be current, usually sometime within the last 4 months. CMV IgM antibody in some women may remain positive for over 4 months (sometimes up to a year or more) or may be a false positive result. Therefore, a third CMV antibody test may be performed, called CMV IgG avidity index. A low CMV IgG avidity index indicates the primary CMV infection occurred less than 4 months prior to the blood test, and a high CMV IgG avidity index indicates a CMV infection occurred 4 months ago or longer.  A CMV IgG avidity test is not recommended if the CMV IgM antibody is negative, and the test cannot be performed if the CMV IgG antibody is negative.

What can be done if I catch CMV during my pregnancy?

If you experience a CMV infection during your pregnancy, your obstetrician should follow the growth and development of your fetus carefully with serial fetal ultrasound examinations and other tests. In addition, consultation with a maternal-fetal medicine specialist or a specialist in high risk obstetrics may be indicated, especially if the effects of in utero CMV are seen in the fetus. At Texas Children’s Hospital Pavilion for Women consultations with a maternal fetal medicine specialist may be requested through this website. Prenatal treatment of the pregnant mother with CMV hyperimmune globulin (CMV enriched antibody) may reduce the transmission of CMV to the fetus and reduce or reverse some of the effects of CMV on the fetus. If you have experienced a primary CMV infection during pregnancy, please consult with your obstetrician or maternal-fetal medicine specialist about whether or not CMV hyperimmune globulin treatment is right for you and your baby, in addition to following the health and well-being of your baby while still in the womb. A national randomized clinical trial is also underway in the United States (and also possibly in other countries in Europe) to more carefully study the potential benefits of this treatment.  More information may be available as well at What if I am pregnant and CMV antibody negative? If you are CMV IgG and CMV IgM antibody negative and pregnant, then you have never had a CMV infection, and are therefore vulnerable to catching CMV for the first time during your pregnancy. By knowing you are CMV negative, and by knowing about the CMV precautions recommended in my first blog post, you may take steps to reduce your CMV risk during pregnancy.

Dr. Gail Demmler-Harrison, Infectious Diseases