Congenital CMV

What is Congenital CMV?

Congenital CMV is an infection that occurs when a baby contracts cytomegalovirus before birth. This happens when a pregnant mother gets infected with CMV and passes the virus through the placenta to her developing baby. CMV is a common virus in the herpes family that affects people of all ages.

Most adults carry CMV without knowing it because their immune system keeps the virus under control. When a mother gets infected with CMV for the first time during pregnancy, her body has not yet built immunity to the virus. This primary infection carries the highest risk of transmission to the baby. About 1 in 200 babies is born with congenital CMV in the United States, making it the most common congenital infection.

Congenital CMV can cause a range of outcomes from no symptoms at all to serious health problems. About 90 percent of babies born with CMV appear healthy at birth. However, some of these babies may develop hearing loss or developmental delays months or years later. The remaining 10 percent have symptoms at birth that can affect the brain, liver, spleen, lungs, and other organs.

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Symptoms

Hearing loss that may worsen over time
Vision problems or eye damage
Small head size at birth
Seizures or tremors
Weakness or difficulty moving muscles
Yellow skin and eyes from liver problems
Purple skin spots or rash
Enlarged spleen or liver
Low birth weight or premature birth
Feeding difficulties in newborns

Most babies with congenital CMV show no symptoms at birth. These babies appear completely healthy in the newborn period. Some may develop hearing loss or learning difficulties later in childhood. Even babies without early symptoms need monitoring for delayed effects.

Causes and risk factors

Congenital CMV occurs when a pregnant woman becomes infected with cytomegalovirus and transmits it to her developing baby. The virus spreads through body fluids including saliva, urine, blood, breast milk, and sexual contact. Women who work with young children face higher risk because toddlers often carry and shed CMV in their saliva and urine. Daycare workers, preschool teachers, and mothers of young children should practice careful hygiene to reduce exposure.

First-time CMV infection during pregnancy poses the greatest danger to the baby. Women who already have CMV antibodies from past infection have much lower transmission rates. However, reactivation of dormant virus or reinfection with a different CMV strain can still affect the baby. Risk factors include caring for young children, having multiple young children at home, working in healthcare settings, and having a weakened immune system. Women planning pregnancy should know their CMV status and take precautions to avoid infection.

How it's diagnosed

Diagnosing congenital CMV requires testing the baby within the first three weeks of life. Doctors collect a sample of the baby's saliva or urine to check for active CMV virus. Blood tests alone cannot confirm congenital infection because antibodies may come from the mother. Testing after three weeks cannot distinguish between congenital infection and infection acquired after birth through breast milk or other exposure.

Pregnant women can be tested for CMV antibodies to determine if they have immunity from past infection. The Cytomegalovirus Antibody test measures IgG antibodies that indicate whether you have been exposed to CMV before. High or rising antibody levels may suggest active infection during pregnancy. Talk to your doctor about specialized testing if you are pregnant or planning to become pregnant and want to understand your CMV status.

Treatment options

Antiviral medication for babies with symptoms at birth to prevent hearing loss
Regular hearing tests every 6 months through early childhood
Vision screening and eye exams to catch problems early
Physical therapy and occupational therapy for developmental delays
Speech therapy if language development is affected
Special education services when learning difficulties appear
Hearing aids or cochlear implants for hearing loss
Early intervention programs starting in infancy

Frequently asked questions

Congenital CMV is an infection that babies get from their mothers during pregnancy. It happens when the cytomegalovirus crosses the placenta and infects the developing baby. About 1 in 200 babies in the United States is born with this infection, making it the most common congenital viral infection.

Congenital CMV cannot be cured, but antiviral treatment can help prevent complications. Babies with symptoms at birth may receive antiviral medication for 6 months to reduce hearing loss and improve developmental outcomes. Early treatment works better than waiting until symptoms develop. Most babies without symptoms at birth do not need treatment but should be monitored.

Babies get congenital CMV when their mother has a CMV infection during pregnancy and the virus passes through the placenta. The risk is highest when a mother gets infected with CMV for the first time while pregnant. Women who already have CMV antibodies from past infection have lower transmission rates but can still pass the virus to their baby.

About 90 percent of babies born with congenital CMV have no symptoms at birth and appear completely healthy. The other 10 percent have symptoms that may include small head size, hearing loss, liver problems, or skin rash. Even babies without early symptoms can develop hearing loss or learning problems later in childhood.

Congenital CMV must be diagnosed within the first three weeks of life through saliva or urine testing. The test looks for active CMV virus in the baby's body fluids. Testing after three weeks cannot confirm congenital infection because babies can catch CMV from breast milk or other sources after birth.

CMV testing during pregnancy is not routine but may be helpful if you work with young children or want to know your immune status. A blood test can show if you have CMV antibodies from past infection. Women without immunity should take extra hygiene precautions during pregnancy. Talk to your doctor about whether testing makes sense for your situation.

Wash your hands frequently with soap and water, especially after contact with young children's saliva or urine. Avoid sharing food, drinks, or utensils with young children. Do not put a child's pacifier in your mouth. Kiss children on the head or cheek rather than on the lips. These simple steps significantly reduce your risk of catching CMV during pregnancy.

Hearing loss is the most common long-term problem from congenital CMV and can worsen over time. Some children develop vision problems, learning disabilities, developmental delays, or seizures. Problems may not appear until months or years after birth. Regular hearing tests and developmental screenings help catch issues early when treatment works best.

Yes, babies with congenital CMV can attend daycare because most children and adults already carry CMV. The virus poses the greatest risk to pregnant women who have never been infected before. Daycare staff who are pregnant should practice good hand hygiene and avoid contact with children's saliva and urine.

Having CMV antibodies from past infection does reduce the risk of transmission to your baby but does not eliminate it completely. Women with existing immunity have about a 1 percent chance of passing CMV to their baby compared to 30 to 40 percent for women with first-time infection. Reactivation of dormant virus or infection with a different CMV strain can still occur.