What is Cytomegalovirus, and how can it be a Problem in Pregnancy?

Cytomegalovirus (CMV) is a virus that can be spread by sexual contact, as well as through contaminated blood, saliva, or urine. While this infection doesn’t usually lead to major problems in adults, it is the most common infection mothers pass to their babies during pregnancy.

CMV infection in adults is usually not a problem. Many people won’t show any symptoms, or they may have vague ones, like fever, aches, and enlarged lymph nodes. Once infected, the virus remains in a person’s body and can cause a recurrent infection at another time.

The rate of pregnant women infected with CMV for the first time varies based on a few things: where she lives, her ethnicity, and her socioeconomic status. In the United States, in general, about 0.7 to 4 percent of pregnant women will contract the virus during pregnancy for the first time, and another 13 percent will have a recurrent infection.

The virus can cross the placenta and infect the baby after an initial or recurrent infection, or during exposure from giving birth or breastfeeding (though it is exposure in the uterus that causes the majority of the problems). In fact, CMV infection is the most common congenital infection in babies. In total, 0.2 to 2.2 percent of newborns are affected by CMV.

CMV can lead to a host of problems in babies, including jaundice, low platelet counts, an enlarged liver, restricted growth, swelling of the heart muscle, abnormal fluid collections throughout the body, deafness, and stillbirth. When a mom is infected for the first time in pregnancy, she has a 30 to 40 percent chance of passing it to her baby, and that risk is highest if she becomes infected in the third trimester. Babies have worse outcomes if they are exposed earlier on in the first trimester. Of those babies severely affected, about 30 percent will die, and up to 80 percent will have lifelong problems from the infection.

Diagnosing CMV in pregnant women can be done with a blood or urine test, usually repeated over a series of a few weeks to see if antibodies to CMV develop. If there are concerns that a fetus is infected (either based on a mother’s symptoms, tests, or abnormal ultrasound findings), an amniocentesis can be done to confirm this, though it is not a perfect test for this kind of infection.

If diagnosed, there are no treatments for either pregnant women or their fetuses. These babies will often be followed more closely with extra ultrasounds and will need to be closely examined after birth.

Since there are currently no vaccines or treatments for CMV, pregnant women are advised to practice good hygiene, including safe sex practices and thorough hand washing. This is especially important for those in frequent contact with young children, who often contract CMV and can spread it.

Sources:

• The American College of Obstetricians and Gynecologists
• Practice Bulletin #151: Cytomegalovirus, parvovirus B19, varicella zoster, and toxoplasmosis in pregnancy
• June 2015.

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