After a choroid plexus cyst (CPC) is found during your baby’s anatomy scan, one of the first questions you may have is:
“Will the cyst disappear?”
For most CPCs detected during the second trimester, the answer is:
Yes, they usually resolve on their own as pregnancy progresses.
But there is something even more important to understand:
A CPC does not need to disappear to prove that your baby is okay.
When a CPC is isolated and prenatal aneuploidy screening is reassuring, whether you can still see the cyst later in pregnancy usually does not change its clinical significance.
What Exactly Is a Choroid Plexus Cyst?
The choroid plexus is normal tissue located within the lateral ventricles of the fetal brain.
It produces cerebrospinal fluid.
During development, small pockets of fluid can become temporarily trapped within folds of the choroid plexus.
On ultrasound, these appear as dark fluid-filled spaces.
We call them:
choroid plexus cysts.
Despite the word cyst, an isolated CPC is not a tumor and does not damage the fetal brain.
Why Do CPCs Disappear?
The fetal brain changes rapidly during pregnancy.
As the choroid plexus develops and its appearance changes, the small fluid-filled spaces that were visible earlier often become smaller and eventually can no longer be seen on ultrasound.
This usually happens naturally.
There is:
no medication
no procedure
and
nothing a pregnant parent needs to do
to make a CPC disappear.
When Do CPCs Usually Disappear?
Most CPCs detected during the mid-trimester resolve later in pregnancy, commonly by the third trimester.
But there is no single week by which every CPC must disappear.
Every pregnancy is different.
And importantly:
The exact timing of disappearance is usually not the clinically important question.
What If the CPC Is Still Visible Later?
This is where parents can become unnecessarily worried.
A CPC that remains visible later in pregnancy does not automatically mean something is wrong with the baby’s brain.
Persistence does not suddenly transform an isolated CPC into a brain malformation.
Instead, clinicians consider the original context:
Was the CPC isolated?
Was the rest of the anatomy scan reassuring?
What did prenatal aneuploidy screening show?
Those questions matter much more.
Do We Need Another Ultrasound to Make Sure It Disappears?
Usually not solely for an isolated CPC when previous aneuploidy screening is negative.
Current SMFM guidance states that when an isolated CPC is found after negative serum or cell-free DNA screening, there is no indication for follow-up ultrasound imaging or postnatal evaluation solely because of the CPC.
This can surprise parents.
It may feel natural to think:
“But shouldn’t we make sure the cyst is gone?”
Clinically, however, seeing it disappear usually does not provide additional information that changes management.
What If I Already Have Another Ultrasound Scheduled?
That’s completely different.
You may have another ultrasound later in pregnancy for many reasons, such as:
- fetal growth assessment
- placental evaluation
- another fetal finding
- incomplete anatomy views
- maternal or obstetric indications
If the choroid plexus is visible during that examination, the CPC may also be reassessed.
But that does not mean the scan was necessary because of the CPC itself.
What If My NIPT Was Low Risk?
If the CPC is isolated and your cell-free DNA/NIPT result is low risk, that is generally a reassuring situation.
An isolated CPC does not override a reassuring screening result.
Current professional guidance does not recommend additional aneuploidy evaluation solely because of an isolated CPC after negative screening.
What If I Never Had NIPT or Other Screening?
That’s a different situation.
If an isolated CPC is identified and you have not previously had aneuploidy screening, your healthcare provider may discuss available screening options.
This may include cell-free DNA/NIPT or serum screening, depending on your circumstances and local practice.
Again, the reason is the historical association between CPC and trisomy 18—not because the cyst is damaging the baby’s brain.
If the CPC Disappears, Does That Rule Out Trisomy 18?
No.
This is an important misconception.
Whether a CPC disappears does not determine whether a fetus has a chromosome condition.
A fetus’s chromosomes do not change because an ultrasound marker disappears.
Likewise:
Persistent CPC ≠ trisomy 18.
The appropriate risk assessment comes from the complete anatomy scan and prenatal screening or diagnostic testing—not from waiting to see whether the cyst disappears.
Does the Size Matter?
Parents sometimes compare measurements:
3 mm
5 mm
8 mm
or worry because there are multiple CPCs.
For an otherwise typical isolated CPC, small differences in size do not tell us whether the baby’s brain will develop normally.
Similarly, CPCs can be:
unilateral
or
bilateral.
Those features should be interpreted in the context of the entire examination rather than used alone to predict aneuploidy.
Can CPCs Grow?
The appearance can vary between examinations.
A CPC may appear:
smaller
similar
or occasionally somewhat different in size depending on the imaging plane and gestational age.
But repeatedly measuring an isolated CPC to track its size is generally not the purpose of prenatal care.
The broader fetal anatomy and screening history are much more informative.
Does My Baby Need Treatment?
No treatment is required for an isolated CPC.
It does not need to be drained or removed.
There is also no evidence-based diet, supplement, activity, or sleeping position that a pregnant parent needs to use to make it disappear.
The natural course is usually simply:
observe fetal development—not treat the cyst.
Will My Baby Need a Brain Scan After Birth?
For an isolated CPC with reassuring prenatal screening, special postnatal imaging is generally not required solely because a CPC was seen during pregnancy.
This is very different from a true structural fetal brain abnormality.
A CPC is primarily a prenatal ultrasound finding rather than a condition that needs ongoing neurological treatment.
What If Other Abnormalities Were Found?
Then the situation is no longer an isolated CPC.
If other structural abnormalities or concerning markers are present, your healthcare team will interpret the complete pattern.
Additional evaluation may include:
- detailed fetal ultrasound
- maternal-fetal medicine consultation
- genetic counseling
- prenatal screening
- diagnostic testing when appropriate
The clinical concern comes from the overall pattern of findings, not from the CPC damaging the brain.
What Should I Ask My Doctor?
If you’re waiting for your baby’s CPC to disappear, consider asking:
- Was the CPC truly isolated?
- Was the rest of the anatomy scan normal?
- Were any other soft markers identified?
- What were my prenatal screening results?
- Does the CPC change my trisomy 18 risk?
- Do I actually need another scan specifically for the CPC?
- If it is still visible later, does that change anything?
- Does my baby need any special evaluation after birth?
The most useful question may be:
“Would anything about my care change depending on whether the CPC disappears?”
For many pregnancies with an isolated CPC and reassuring screening, the answer is:
No.
Key Takeaway
Most choroid plexus cysts disappear naturally before birth.
But the bigger message is:
CPC does not need treatment.
CPC does not need to disappear to prove the brain is normal.
Persistent CPC does not mean trisomy 18.
Disappearance does not rule out a chromosome condition.
And when an isolated CPC is found after reassuring prenatal aneuploidy screening, another ultrasound is generally not needed solely to document that the cyst has disappeared.
So instead of focusing only on:
“Is the cyst gone?”
focus on what matters more:
“Was it isolated, was the anatomy scan reassuring, and what did my prenatal screening show?” 🧠👶
About the Author
This article was written by a sonographer with over 20 years of hands-on clinical ultrasound experience, including fetal, breast, and thyroid imaging. In practice, parents often understandably focus on whether a CPC has disappeared. But the more meaningful information comes from the complete anatomy scan and prenatal screening—not from repeatedly measuring a temporary cyst. My goal is to help parents understand which ultrasound findings actually change clinical care.
This article is for general educational purposes and does not replace individualized prenatal diagnosis, genetic counseling, or medical advice from your healthcare provider.
