Ask Dr. K: Herpesvirus CMV can pass to fetus

DEAR DOCTOR K: At a recent pregnancy checkup, my doctor said something about cytomegalovirus. What is that, and what does it have to do with pregnancy?

DEAR READER: CMV is one of eight members of the family of human herpesviruses. The first two members are the viruses that cause “herpes” sores of the mouth, genitals and other areas.

All of the herpesviruses cause a lifelong infection. Once you are infected with CMV, it always remains in your body, generally causing no trouble. Up to 85 percent of adults in the United States have been infected. The virus can pass from person to person through body fluids such as blood, urine or saliva. Women can pass CMV to their unborn babies in the womb, in vaginal secretions during delivery and in breast milk after birth.

In most healthy adults and children, a new infection with CMV results in only mild and temporary symptoms. In fact, a new infection often is “silent,” causing no symptoms at all.

But CMV can be serious, and even fatal, for newborn babies. That’s why, if you are pregnant, your doctor may want to test you for CMV.

When a pregnant woman becomes newly infected with CMV during pregnancy, there is a 40 percent chance her baby will become infected. In contrast, less than 2 percent of babies born to mothers who were infected with CMV before they became pregnant are infected. And their problems tend to be less severe.

CMV infection in newborns whose mothers were infected during pregnancy can cause serious disability. Some babies may die from the infection, but others may have no long-lasting effects.

Newborns with CMV are likely to be born premature and at a low birth weight. They may be born with a small brain or other nervous system disorders that can cause seizures, deafness, mental disability or death. CMV can cause the liver and spleen to enlarge, liver abnormalities that cause yellowing of the skin and eyes, and blood disorders.

Parents, including expectant mothers, can become infected from their children, though. CMV does not spread easily.