Sonographically detected fetal choroid plexus cysts. Frequency and association with aneuploidy.

Over a 22-month period, 1045 second-trimester pregnancies were evaluated with ultrasound for the presence of choroid plexus cysts. The frequency of fetal choroid plexus cysts was 3.6% (38/1045). The outcome of the 38 fetuses possessing choroid plexus cysts was as follows: One fetus had triploidy, an occurrence not previously reported; one fetus had hydrocephalus and a normal karyotype; the other 36 fetuses were born normal. Our data were combined with those of previously reported series of fetal choroid plexus cysts to determine if chromosomal analysis is necessary in all fetuses possessing a choroid plexus cyst.