In congenital CMV disease, a baby is infected with the CMV virus. This happens during pregnancy or shortly after birth. The virus is common but does not make most children sick.

About 40% of the Dutch population carry the CMV virus, usually without this being noticed. Sometimes it causes fatigue, muscle pain, mild fever or a general feeling of sickness - symptoms that can also occur during a normal pregnancy. So a pregnant woman often does not know she has a CMV infection herself.

In the Netherlands, 1 in 100 pregnant women becomes infected with CMV. About 40% of these women pass CMV to their baby. Every year, 1,000 babies are born with congenital CMV disease. That is 1 in 250 children.

In 90% of babies with congenital CMV disease, there are no or mild symptoms. But 1 in 8 children do develop symptoms, sometimes at birth, sometimes later. Examples:

· Hearing impairment or deafness

· Developmental delays

· Learning difficulties, behavioral problems

· Epilepsy

· Vision impairment

· Muscle problems or spasticity

Most children have a normal life expectancy. Only children with severe symptoms have a shorter lifespan.

The virus can reach the unborn child via the placenta.

· If the mother becomes infected during the first three months of pregnancy, there is approximately a 30% chance that the baby will also be infected.

· If infected in the last three months, this rises to approximately 70%.

The CMV virus may affect the child's brain. The baby's body can also react by making the liver and spleen work extra hard, which can lead to a swollen belly. Early infection in pregnancy increases the likelihood of symptoms in the baby.

Sometimes the virus does not directly infect the child but damages the placenta. This can reduce blood flow to the child, leading to poor growth and a low birth weight.