THE ISOLATED CHOROID-PLEXUS CYST

Objective: To describe the karyotypes of a population of fetuses with choroid plexus cysts and compare affected fetuses with and without add itional ultrasonographic findings. Methods: The study population inclu ded all patients undergoing second-trimester ultrasound examination in a prenatal diagnostic program between January 1993 and October 1995. The records of all cases in which a choroid plexus cyst was found were reviewed, and information was abstracted regarding the fetal karyotyp e and the presence of other sonographic abnormalities. Results: Two hu ndred ten cases of choroid plexus cysts were identified among 7617 pat ients (2.8%) who underwent second-trimester ultrasound examination. Th e majority of the cases (181, or 86%) involved isolated choroid plexus cysts and the remaining 29 (14%) were associated with additional ultr asonographic findings. Autosomal aneuploidy was found in one patient w ith an isolated choroid plexus cyst (trisomy 21) and in another with a dditional findings (trisomy 18); the mothers of both of these patients were at least 35 years old. For those fetuses with known outcome, the risk of aneuploidy with isolated choroid plexus cyst (one in 180) was not statistically significantly different from that associated with c horoid plexus cyst accompanied by other sonographic findings (one in 2 6). More than 1000 fetuses with choroid plexus cysts would have to be studied to determine whether such a difference was real. Conclusion: B ecause of the rarity of aneuploidy, the reported risk for a fetus with an isolated choroid plexus cyst must be interpreted cautiously and sh ould include the baseline risk. (Obstet Gynecol 1998;92:232-6. (C) 199 8 by The American College of Obstetricians and Gynecologists.)