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The information in this leaflet only applies if ventriculomegaly was the only finding on the scan. Every woman in Wales is offered a fetal anomaly scan when they are between 18 and 20 weeks pregnant. The aim of this scan is to:

  • check your baby's physical development;
  • help detect structural abnormalities, for example spina bifida and heart defects;
  •  check the amount of water around the baby in the womb; and
  •  look at the position of the placenta.

The finding from your scan does not necessarily mean that your baby has a problem with any of their organs.

Published January 2022, 4th edition.


― Ventriculomegaly
What is ventriculomegaly?
― What will happen next?
― What tests will I be offered?
― Further information





Ventriculomegaly is found in approximately 1 in every 1,000 (0.1%) pregnancies in Wales.

What is ventriculomegaly?

Ventricles are normal spaces within the baby’s brain which are filled with liquid (cerebrospinal fluid, or CSF) which acts as a ‘cushion’ for the brain and also provides nutrients to the brain.

Normally the ventricles are less than 10.1 millimetres (mm) wide. When they measure between 10.1mm and 15.1mm, this is known as ventriculomegaly. This can be caused by too much fluid being produced in the brain. When the ventricles measure more than 15.1mm on the anomaly scan this is known as hydrocephalus.

In Wales, when ventriculomegaly has been seen as the only abnormality on the 18 to 20 week scan, about 5 in every 10 babies (50%) are born with no other problems. Of the other 5 in 10: On average, 4 in every 10 babies (40%) with ventriculomegaly will have a brain abnormality which may delay their development. About 1 out of 10 pregnancies (10%) with ventriculomegaly will have a chromosomal abnormality.

In general, the outcome is worse when the ventricles are larger, there are other anomalies seen on the scan, and if the baby has a chromosomal abnormality. Occasionally, infections such as cytomegalovirus (CMV), toxoplasmosis and rubella (German measles) are associated with ventriculomegaly.

In Wales from 2011 to 2018, there were four recorded cases of CMV linked with ventriculomegaly, one case of toxoplasmosis and no known cases of German measles.

What will happen next?

You will be seen by a midwife who specialises in antenatal screening or your hospital doctor (obstetrician) who will explain what care you will be offered next. Because of these findings you will be offered an appointment with a fetal medicine consultant.

This appointment may or may not be at the hospital where you are booked to deliver your baby. At this appointment the midwife and doctor will explain more about the conditions and about the tests you can have and how they are done.

Some women decide not to have these tests. The midwife and doctor will support whatever choice you make. You may have questions to ask the midwife or doctor and may want to have another appointment. You may want your partner or a friend to come with you, and you may want more time to think before you decide what to do next.

You may want to think about what you might do if the test result shows your baby has one of the conditions. Some women will want to prepare themselves for the birth knowing that their baby has been shown to have a problem.

Other women may decide to end the pregnancy if a poor outcome is expected.

What tests will I be offered?

  • A blood test

You will be offered a blood test to see if you have recently had CMV, toxoplasmosis or rubella (German measles).

If the blood test shows you have had any of these infections, there is a small chance the infection may pass across the afterbirth and infect your baby.

If your baby is infected with any of the above it may cause problems such as low birth weight, jaundice, hearing loss, sight loss and heart abnormalities.

  • Amniocentesis

You will be offered an amniocentesis if you want to know before your baby’s birth if the ventriculomegaly is because of a chromosomal abnormality.

 An amniocentesis is a very accurate way of telling whether your baby does or does not have these conditions. If you have an amniocentesis there is a 0.5% chance that you could have a miscarriage (this means that one in every 200 women could lose their baby as a result of an amniocentesis). The miscarriage can be the loss of a baby that was affected or unaffected with the conditions.

If your blood test has shown that you have had a recent infection an amniocentesis will also tell if your baby is infected by CMV, toxoplasmosis or rubella (German measles).

You can get more information about amniocentesis from the Antenatal Screening Wales booklet ‘Information for women offered further tests for suspected chromosomal conditions.’

  • MRI scan of your baby’s brain

You will be offered an MRI scan of your baby’s brain. This will give more information about how your baby’s brain is developing.

Further information

You can get more information from the hospital midwife who specialises in antenatal screening or your hospital doctor (obstetrician).

Antenatal Results and Choices (ARC)

Helpline: 0845 077 2290 or 0207 713 7486 from a mobile



CMV action

Phone: 0808 802 0030




Phone:0300 330 9250




Information from CARIS (Congenital Anomaly Register and Information System) and The Welsh Study of Mothers and Babies.