At the 20-week scan, your sonographer looks carefully at your baby’s brain. Sometimes one or more small, round, fluid-filled spaces are seen in a structure inside the brain called the choroid plexus. These are called choroid plexus cysts, often shortened to CPCs.
In most pregnancies, choroid plexus cysts are a normal finding. They disappear on their own later in pregnancy and do not affect the baby’s brain, development or intelligence.
When they are present on their own, as an isolated finding, choroid plexus cysts are not associated with any underlying chromosomal condition, and they resolve by themselves. The rest of the scan and your earlier screening results are reviewed carefully to confirm that they are isolated.
Key points
- Choroid plexus cysts are small fluid-filled spaces in the choroid plexus, the part of the brain that makes the fluid around the brain and spinal cord.
- They are seen in about 1 to 2 in 100 babies at the 20-week scan.
- They are more common at 18 weeks than at 20 or 22 weeks, and as an isolated finding they almost always resolve by 28 to 32 weeks.
- They do not damage the brain and do not affect your baby’s development or intelligence.
- As an isolated finding, with a low-chance screening result, choroid plexus cysts do not increase the chance of a chromosomal condition.
- They are not a marker for Down’s syndrome. When choroid plexus cysts are seen in babies with a chromosomal condition, there are always other abnormalities on the scan or a high-chance screening result.
- A specialist fetal medicine review brings together the scan findings and your earlier screening to decide whether anything further is needed.
What are choroid plexus cysts?
The brain contains fluid-filled spaces called ventricles. Inside them is a soft, spongy structure called the choroid plexus, which makes the fluid that surrounds and protects the brain and spinal cord.
As the choroid plexus develops, a little of this fluid can become trapped within it, forming a small, round, fluid-filled space. On the scan, this appears as a dark circle within the bright choroid plexus. This is a choroid plexus cyst.
Despite the name, choroid plexus cysts are not cysts in the brain tissue itself, and they are not a growth or a tumour. They are a temporary feature of how the choroid plexus develops.
How common are they?
Choroid plexus cysts are seen in about 1 to 2 in 100 babies at the 20-week scan.
How often they are seen depends on the stage of pregnancy. They are a normal part of how the choroid plexus develops, so they are more common at 18 weeks than at 20 or 22 weeks. As an isolated finding, they almost always resolve by 28 to 32 weeks.
In the NHS screening programme in England, choroid plexus cysts are not reported as a soft marker on their own, because they are so common in healthy babies.
Are isolated choroid plexus cysts of any significance?
No. Isolated choroid plexus cysts are of no consequence, as they are part of normal brain development.
When they are seen in isolation, without any other structural or anatomical abnormality, and with a low-chance result from combined screening in the first trimester or from NIPT, choroid plexus cysts are of no clinical significance.
Does it matter if they are on one side or both?
No. Choroid plexus cysts can be present on one side of the brain or on both sides. Neither their presence on both sides, nor their size, nor their position in the choroid plexus, towards the front or the back of the brain, makes a difference.
This applies provided that the cysts are isolated, and provided that the diagnosis of choroid plexus cysts is correct and another abnormality of the brain has not been mistaken for them. This is one reason why an assessment by a fetal medicine specialist is helpful.
Do they go away?
Yes. Choroid plexus cysts almost always disappear on their own as the choroid plexus matures, almost always by 28 to 32 weeks of pregnancy. Even when small cysts are still seen after birth, they are not linked to any problems with the baby’s health or development.
When choroid plexus cysts are an isolated finding and your screening result was low chance, a follow-up scan to check that they have gone is not usually needed.
Will they affect my baby’s brain or development?
No. Choroid plexus cysts do not press on or damage the brain, and they do not affect how the brain develops. Studies following up children who had choroid plexus cysts have shown normal development, and no treatment is needed before or after birth.
Are they linked to a chromosomal condition?
Choroid plexus cysts are not a marker for Down’s syndrome. Their main link is with a rarer chromosomal condition called Edwards’ syndrome (trisomy 18).
As an isolated finding, with no other associated findings and a low-chance screening result, choroid plexus cysts do not increase the chance of Edwards’ syndrome.
In pregnancies where choroid plexus cysts are associated with a chromosomal condition, they are always associated with other abnormalities, such as heart problems, clenched hands, unusual feet or slow growth, or with a high-chance result from combined screening. In this situation, the main clinical finding is not the choroid plexus cysts but the other abnormalities, and it is these that determine the outcome for the baby.
However, a holistic fetal medicine review is essential. This includes a detailed assessment of your baby’s anatomy, a careful check for any other associated markers, and a review of your first-trimester chance of chromosomal conditions from combined screening, which assesses the chance of Edwards’ syndrome as well as Down’s syndrome. If you have had NIPT, this result is also taken into account.
For further information, read: Genetic Markers and Soft Markers at the 20-Week Scan
What happens next?
What is recommended depends on the whole picture, not on the cysts alone. As a general guide:
| Situation | What it usually means | Usual next step |
|---|---|---|
| Isolated choroid plexus cysts, low-chance combined screening or NIPT | A normal finding | No further tests or follow-up scans are usually needed |
| Isolated choroid plexus cysts, no earlier screening | Very likely a normal finding | Discussion of NIPT for reassurance |
| Choroid plexus cysts with other markers or structural findings | A higher chance of a chromosomal condition | Specialist fetal medicine review and discussion of amniocentesis |
If an amniocentesis is offered, the sample is usually tested with a detailed chromosome test called a microarray, which can look for small chromosome changes as well as conditions such as Edwards’ syndrome.
Choroid plexus cysts do not change how or where you give birth, and your baby does not need any special checks after birth because of them.
Frequently asked questions
Did I do something to cause this?
No. Choroid plexus cysts are a normal part of how the brain develops in some babies. They are not caused by anything you have eaten, drunk or done during pregnancy.
Are choroid plexus cysts a brain abnormality?
No. They are small pockets of fluid in the choroid plexus, not in the brain tissue, and they do not affect how the brain develops or works.
Will I need another scan to check they have gone?
Not usually. When the cysts are an isolated finding and your screening result was low chance, a follow-up scan is not normally needed. You may still be offered scans for other reasons.
Do I need an amniocentesis?
Not usually. When choroid plexus cysts are an isolated finding and your earlier screening was low chance, a diagnostic test is not recommended. It may be discussed if other findings are seen.
Our approach at The Pregnancy Clinic
At The Pregnancy Clinic in Sevenoaks, Kent, detailed scans are carried out by fetal medicine specialists. If choroid plexus cysts are seen, our approach includes:
- a detailed assessment of your baby’s brain, heart, hands, feet and the rest of the anatomy
- a careful check for any other associated markers
- a review of your earlier combined screening or NIPT results
- a clear explanation of the findings on the day, including whether any further tests would be helpful
- a written report to share with your NHS maternity team.
Book a detailed scan
If choroid plexus cysts were seen at your scan and you would like a specialist review, a detailed anomaly scan with a fetal medicine specialist can assess your baby’s anatomy and give you a clear picture.
Book a detailed anomaly scan →The Pregnancy Clinic provides planned appointments only. If you have pain, bleeding, leaking fluid, reduced baby movements or any other urgent concern, please contact your local NHS maternity unit straight away, or call 999 in an emergency.
Related pregnancy guides
Clinical references
- Society for Maternal-Fetal Medicine; Prabhu M, Kuller JA, Biggio JR. Consult Series #57: Evaluation and management of isolated soft ultrasound markers for aneuploidy in the second trimester. Am J Obstet Gynecol 2021;225:B2–15
- Shirazinejad S, Moradi H, Khanjani S. Natural history and prognostic significance of fetal choroid plexus cysts: a systematic review. BMC Pregnancy Childbirth 2026;26
- Cai M, Huang H, Su L, et al. Choroid plexus cysts: single nucleotide polymorphism array analysis of associated genetic anomalies and resulting obstetrical outcomes. Risk Manag Healthc Policy 2021;14:2491–7
- Hung KL, Liao HT. Neonatal choroid plexus cysts and early childhood developmental outcome. J Formos Med Assoc 2002;101:43–7
This guide provides general information and does not replace individual medical advice. Recommendations may vary according to your scan findings, pregnancy history and clinical circumstances.