Cytomegalovirus and pregnancy

Cytomegalovirus (CMV) is a common virus of the herpes family. Most people become infected with this virus at some point. The infection usually causes no symptoms and goes completely unnoticed. It can, however, be serious for a developing fetus, infants whose immune systems are still developing, and people of all ages whose immune systems are not functioning properly (for example, those who have HIV or AIDS).


Causes/associated factors
When a person is infected with CMV for the first time, symptoms may or may not appear. Once the infection clears up, the virus remains dormant (inactive) in the body and can cause a second infection later -- often when the person's immune system is not functioning well. Again, the second infection may or may not have symptoms.
Depending on where you live, between 50 and 85 percent of women have already had a CMV infection when they become pregnant. About 1 percent of these women will have a recurrent infection during the pregnancy. Of those women who have never had a CMV infection, 1 to 3 percent will develop the infection during the pregnancy. Up to 40 percent of those who become infected will pass the infection to their unborn babies.


CMV and infants
Cytomegalovirus is the leading cause of infection for the developing fetus. From .5 to 2 percent of infants in the United States are born with a CMV infection. Of these infants, up to 15 percent will eventually be diagnosed with problems such as mental retardation and deafness. Another 10 percent are born with symptomatic CMV infection (also known as cytomegalic inclusion disease, CID). Some of these symptomatic infants will not survive. For the developing fetus, the risk of developing symptomatic infection is greatest if the mother contracts CMV for the first time during the first half of pregnancy. If she develops a recurrent infection during pregnancy, the risk of serious disease in the fetus is minimal. Premature infants also have a greater risk of developing serious illness. Infants who acquire the CMV infection during or after delivery usually develop no symptoms or long-term consequences.

Transmission
Cytomegalovirus spreads through direct contact with infected body fluids, including saliva, nasal secretions, urine, semen, cervical or vaginal secretions, blood and breast milk. Exposure to the virus may occur during such activities as infant care (such as diaper changes, feeding and bathing), sexual contact, blood transfusions or organ transplantation. During pregnancy, the virus can spread from the mother to the fetus through the placenta (a structure that develops in the womb to nourish the fetus and help it discard waste). A mother can also transmit the infection to the baby during childbirth through infected cervical secretions, and after birth the infection can be transmitted through breast milk. The incubation period (the time from exposure until symptoms appear, if they appear at all) is usually from 28 to 60 days.
It is unknown exactly how long the virus may be transmitted to others after an active infection. The virus may be shed in the person's urine and saliva for many months. An infected newborn may first shed the virus for as long as five or six years -- adults appear to shed the virus for a shorter time. Excretion of the virus may recur if the person develops a weak immune system.


Signs/symptoms
Symptoms of a CMV infection vary depending on the age and health of the person affected. Again, the infection typically goes unnoticed because often there are no symptoms, especially for children. For adults, the infection may cause an illness that resembles mononucleosis. Symptoms may include:
swollen lymph glands
fever
fatigue
rash
sore throat
mild liver and spleen enlargement
More serious illness is rare, but possible -- especially for people whose immune systems are not functioning properly. They may experience:

myocarditis (inflammation of the heart muscle)
pneumonitis (inflammation of the lungs)
meningitis (inflammation of the membranes surrounding the brain and spinal cord)
thrombocytopenia (a blood clotting disorder that can cause excessive bleeding)
anemia (a condition characterized by a low number of red blood cells or hemoglobin, a protein in the red blood cells that contains iron)
chorioretinitis (inflammation of parts of the eye that can cause loss of vision)
About 10 percent of infants born with a CMV infection have serious symptoms at birth, which may include a combination of:

low birth weight
microcephaly (abnormally small head)
brain damage resulting in mental and motor retardation
petechiae (purplish spots under the skin caused by abnormal bleeding)
hepatosplenomegaly (enlargement of the liver and spleen)
jaundice (yellowing of the skins and whites of the eyes)
pneumonitis (inflammation of the lungs)
deafness
chorioretinitis (inflammation of parts of the eye that can cause loss of vision)
anemia (a condition characterized by a low number of red blood cells or hemoglobin, a substance in the red blood cells that contains iron)
Up to 15 percent of infected infants who have no symptoms at birth will develop problems later on, which may include hearing loss, learning disabilities, mental retardation, motor developmental delays, lost or diminished vision, and seizures. Infections spread to an infant during or after birth usually don't cause symptoms, but some affected infants may later develop pneumonia (a lung infection) due to the CMV infection.


Diagnosis
Diagnosis in the mother
It can be tough to diagnose a CMV infection during pregnancy due to the nature of the illness, which may have no symptoms. If a CMV infection is suspected, it can be difficult to determine if the infection is new or recurrent.

The body normally produces antibodies to fight infection. These antibodies can be measured with blood tests. For the cytomegalovirus, however, it is difficult to determine if antibodies indicate a past infection, an active new infection or an active recurrent infection. Several blood tests may be done at different times to compare the results. If the amount of antibodies increases between tests, for example, it may indicate an active infection. To complicate the situation, however, some people with CMV infections do not test positive for the antibody.

Cytomegalovirus can also be detected in body fluids with a viral culture. Although this lab test confirms there has definitely been a CMV infection, it can't distinguish between a recent infection and one that occurred months or even years earlier. A combination of tests may be needed to help establish the diagnosis.

Diagnosis in the fetus
When a pregnant woman has been diagnosed with a CMV infection, the doctor may attempt to determine if the fetus has been infected. Tests may include:

amniocentesis (taking a sample of the amniotic fluid, which protects the fetus in the womb) to test the amniotic fluid for the virus
cordocentesis (taking a sample of fetal blood from the umbilical cord) to test the fetal blood for antibodies to CMV
ultrasound (using sound waves to create images of internal body parts) to identify any evidence of birth defects or delayed growth
Diagnosis in the infant
Infants who are infected during or after birth won't shed the virus in body fluids for three to 12 weeks. If a culture of body fluids is positive within one week after birth, the infant was infected while in the womb. Some infants also have CMV antibodies in their blood. For infants who are severely ill, other diagnostic blood tests, X-rays or imaging studies may be necessary.


Treatment
There is currently no effective medical treatment for CMV during pregnancy. The use of antiviral medications is being studied in infants.

Complications
Again, complications of CMV contracted before birth include hearing loss, mental retardation, learning disorders, motor and developmental delays, loss of vision or diminished vision, and seizures.

Prevention
There is currently no vaccine that offers protection from CMV. If you're pregnant or plan to become pregnant, especially if you work with children, learn the risks of a CMV infection and get tested for CMV antibodies. If you test positive, the risk of your fetus developing a serious infection is low. If you test negative, however, protect yourself from exposure to the virus.
Avoid contact with potentially infected body fluid, including urine, saliva and nasal secretions, when possible. Be especially careful when kissing children or wiping their noses.

Wash your hands with warm water and soap often, but especially after contact with any body fluids. For example, make sure you wash your hands after changing diapers, helping a child in the rest room, or handling saliva-covered toys. Avoid touching your mouth or nose before you've washed your hands.

If you're a health care worker, strictly follow standard universal precautions.
If you're diagnosed with a cytomegalovirus infection, wait at least six months before becoming pregnant. Don't breastfeed a premature or ill infant if the infant does not have antibodies against CMV. Although it's safe to nurse a healthy full-term infant, discuss the issue first with your baby's doctor.