Fetal neurosonogram: a detailed scan of your baby's brain and spine

Medically written by Dr. Sushma Dhakal, MBBS · MD (Obstetrics & Gynaecology) · Fellowship in Fetal Medicine · Updated 30 October 2026 · 3 min read

A fetal neurosonogram (neurosonography) is a specialised ultrasound of the baby's brain and spine. The routine anomaly scan checks a few standard views of the head. A neurosonogram goes further, looking at the brain in several planes to assess its structures in detail.

When is it recommended?

A finding on the anomaly scan, such as ventriculomegaly (fluid spaces in the brain measuring 10 mm or more), a small or large head, or a difference in the back part of the brain (posterior fossa).
When the cavum septi pellucidi (a normal midline fluid space) or part of the corpus callosum is not clearly seen.
A previous child or family member with a brain or spine condition.
Infections in pregnancy that can affect the brain (such as cytomegalovirus or toxoplasmosis), or complications in monochorionic twins.
A suspected spine problem such as spina bifida.

When and how is it done?

A neurosonogram is usually done from about 20 weeks, and often repeated around 28–32 weeks, because the brain keeps developing throughout pregnancy. When the baby's head is low in the pelvis, a transvaginal scan can give much clearer pictures of the brain; this is safe for the baby. An abdominal approach is used when the head is higher up. The scan takes 30–60 minutes.

What does it look at?

The ventricles (fluid spaces) and their size.
Midline structures: the corpus callosum and cavum septi pellucidi.
The cerebellum and posterior fossa.
The developing folds of the brain surface (sulci and gyri), which form gradually in the second half of pregnancy.
The spine along its full length, and the skin covering it.

Limitations

Some features of the brain, especially the surface folds and some midline structures, only become visible later in pregnancy, so a normal scan at 20 weeks cannot exclude every condition. Image quality depends on the baby's position. In some situations a fetal MRI, usually after 28 weeks, gives additional information and may be recommended.

If something is found

Many findings, such as mild isolated ventriculomegaly, turn out to have a good outlook, while others need more tests. Depending on the finding, you may be offered genetic testing (amniocentesis with microarray), blood tests for infection, follow-up scans and a consultation with a paediatric neurologist or neurosurgeon. You will be given time to understand the results and your options, with honest and compassionate counselling.

Have questions about your pregnancy?

Book a consultation with Dr. Sushma Dhakal, Fellowship-trained fetal medicine specialist (FMF UK certified).

Book this scan Request Counselling

Frequently asked questions

How is a neurosonogram different from the anomaly scan?

The anomaly scan checks a few standard brain views. A neurosonogram examines the brain and spine in detail in several planes.

Is a transvaginal brain scan safe for the baby?

Yes. It is a gentle ultrasound and is safe in pregnancy.

What is ventriculomegaly?

Enlarged fluid spaces in the baby's brain, 10 mm or more. Mild isolated cases often have a good outlook but need further assessment.

Will I need a fetal MRI?

Sometimes. MRI after about 28 weeks can add information when the scan shows a finding or views are limited.

This guide is for general information only and is not a substitute for personal medical advice. Every pregnancy is different. Please consult your doctor about your own situation. In an emergency, go to the nearest hospital.