Objectives: Choroid plexus cysts are commonly found at the time of a routine second-trimester scan, but there is much debate as to their clinical significance. The aims of this study were to define the incidence of choroid plexus cysts in an unselected population and describe their association with aneuploidy.
Design: This was a prospective, observational multicenter study.
Subjects: Subjects were all fetuses found to have choroid plexus cysts with a maximum diameter of 3 mm or greater and who were between 14 and 24 weeks' gestation when scanned in the routine ultrasound department at any of the 13 participating hospitals.
Results: There were 658 fetuses with choroid plexus cysts in a total of 101,600 births. The overall incidence of aneuploidy was 2.1%, but in fetuses with isolated choroid plexus cysts the incidence of proven aneuploidy was 0.5% (95% confidence interval (CI), 0.1-1.4%). If age is taken into consideration, then the incidence of aneuploidy in fetuses with isolated choroid plexus cysts where the mother is under the age of 36 years was 0.36% (95% CI, 0.04-1.3%), and 2.4% (95% CI, 0.06-12.6%) in older women.
Conclusions: We conclude that the presence of choroid plexus cysts increases the risk for aneuploidy, mainly trisomy 18. In the majority of cases, the final risk will remain small, but will increase as maternal age increases.