What are the implications and recommendations for a fetus with a choroid plexus cyst?

Management of Choroid Plexus Cysts

For pregnant patients with isolated choroid plexus cysts (CPCs) and negative aneuploidy screening (serum or cell-free DNA), no further aneuploidy evaluation is needed, as this finding is a normal variant with no clinical importance and requires no follow-up ultrasound or postnatal evaluation. 1, 2

Understanding the Finding

• CPCs are small, fluid-filled structures within the choroid of the lateral ventricles that appear as echolucent cysts, typically measuring <1 cm in diameter 2
• They may be single or multiple, unilateral or bilateral, and nearly all resolve spontaneously by 28 weeks gestation 2
• CPCs are not structural or functional brain abnormalities 2

Risk Assessment for Aneuploidy

Association with Trisomy 18

• CPCs are present in 30-50% of fetuses with trisomy 18 2
• However, when trisomy 18 is present, multiple structural anomalies are almost always evident (structural heart defects, clenched hands, talipes deformity, fetal growth restriction, polyhydramnios) 2
• For truly isolated CPCs (without other abnormalities), the likelihood ratio for trisomy 18 is <2, indicating minimal risk 2

No Association with Trisomy 21

• The presence of a CPC does not alter the risk of trisomy 21 2

Management Algorithm

If Patient Has Already Had Negative Aneuploidy Screening

No further evaluation is warranted: 1, 2

• No additional aneuploidy testing needed
• No follow-up ultrasound imaging required
• No postnatal evaluation necessary
• Reassure the patient this is a normal variant

If Patient Has Not Had Aneuploidy Screening

Perform detailed ultrasound to confirm the CPC is truly isolated: 2

• Carefully evaluate for structural anomalies, particularly cardiac defects, hand positioning, clubfoot, and growth restriction
• If other anomalies are present, this is NOT an isolated CPC and warrants different management

Counsel regarding minimal increased risk of trisomy 18: 1, 2

• Offer noninvasive aneuploidy screening with cell-free DNA (cfDNA) 1, 2
• If cfDNA is unavailable or cost-prohibitive, offer quad screen 1, 2
• Do not recommend invasive diagnostic testing (amniocentesis) solely for isolated CPCs 2

If Patient Previously Declined Aneuploidy Screening

• Each practice should establish a standardized protocol for how isolated soft markers will be documented and managed 1
• Patients should be informed before the ultrasound examination of how findings will be handled 1
• Some providers may treat isolated CPCs as normal variants and not discuss them (except to document), while others may use this as an opportunity to re-offer aneuploidy screening 1

Critical Pitfalls to Avoid

Overreacting to isolated CPCs leads to unnecessary procedure risks: 2

• Amniocentesis carries a procedure-related pregnancy loss risk
• Historical data suggesting 1-2% aneuploidy risk 3, 4 predates modern aneuploidy screening and included patients with advanced maternal age or abnormal serum screening
• One older analysis concluded that for every one infant with trisomy 18 detected, 25 normal fetuses would be lost due to amniocentesis complications 5

Ordering unnecessary follow-up imaging: 2

• When aneuploidy screening is negative, no follow-up ultrasound is needed for isolated CPCs
• CPCs resolve spontaneously and do not require documentation of resolution

Failing to distinguish isolated from non-isolated CPCs: 2

• The presence of other structural abnormalities fundamentally changes the risk assessment
• A detailed anatomic survey is essential before labeling a CPC as "isolated"