Ventriculomegaly
Ventriculomegaly
Patient Information
Maternity Service
- Author ID: JR
- Leaflet Ref: Mat 012
- Version: 1
- Leaflet title: Ventriculomegaly
- Date Produced: October 2025
- Expiry Date: October 2027
What does Ventriculomegaly mean?
In the brain, there are five fluid-filled spaces called ventricles. Ventricles make, and are filled with, cerebrospinal fluid that surrounds and moves around the brain and spinal cord. This fluid cushions and protects the brain and nerves in the spinal cord and protects them from damage
There are two such ventricles, one on either side of your baby’s brain called lateral ventricles, that are routinely measured during your mid-trimester anomaly scan (around 20 weeks.)
The normal width of each of the two lateral ventricles is less than 10mm. If the radiographer finds that one or both of these ventricle’s measure 10mm or more, then this is called ventriculomegaly. Ventriculomegaly occurs in about 1% of babies. Up to 12mm is considered mild, up to 15mm is moderate and above 15mm is severe.
What causes Ventriculomegaly?
In most babies with ventriculomegaly this is a normal variation, and after further investigations we can reassure you that all is satisfactory.
However, other cases of ventriculomegaly may include:
- Infections such as toxoplasmosis and cytomegalovirus
- Underlying anomalies in the brain or obstruction
- Underlying chromosomal or genetic anomalies
- Bleeding in the brain, which is rare
What happens if I am told my baby has Ventriculomegaly?
You will be referred for a Fetal Medicine scan, which could be at Thomas Linacre Centre or St Mary’s Hospital in Manchester. At this appointment, the consultant will perform a detailed ultrasound scan of your baby. This is to look for any findings which may explain the reason for the extra fluid in your baby’s brain. You will be offered a blood test to rule out certain infections that can lead to ventriculomegaly.
You will be offered further invasive testing called amniocentesis, which involves taking a sample of the amniotic fluid around your baby. This is a test which checks your baby’s chromosomes to see if there is an unexpected finding, such as Down syndrome, which could cause the extra fluid. It will check all of the chromosomes, and the full result takes around 2 weeks. The link below will take you to patient information about amniocentesis. Please ignore the section relating to CVS, as this would not apply to you.
If the increased fluid persists, you may be offered an MRI to look in detail at your baby’s brain structure.
You may have further ultrasound scans to monitor any changes in the size of your baby’s lateral ventricles.
What does this mean for when my baby is born?
The outcome for your baby will depend on factors such as if there is an underlying cause, or the severity of the condition. We will involve the neonatal doctors, who may want to have a discussion with you about a further management plan after your baby has been born.
It is difficult to provide parents with reliable figures regarding the chance of a neurological problem after birth in a baby diagnosed with ventriculomegaly during pregnancy. Although there is still insufficient data, research indicates that the risk of a neurological impairment is not higher than 10% when the ventriculomegaly is mild and isolated. This is about the same as the rest of the population.
If you have any questions, please contact the screening midwives on 0300 707 5696 and they will discuss the scan findings further.
Last modified 28th June 2026 16:30:54 pm