Fetal lateral ventricle choroid plexus cysts: the dilemma of amniocentesis.

Although lateral ventricle choroid plexus cysts in the second-trimester fetus have been considered a benign developmental phenomenon of no clinical significance, an association with trisomy 18 has been suggested. We designed a prospective study to determine whether karyotype analysis is indicated when such cysts are encountered on prenatal sonogram. During a 20-month period, 5400 low-risk pregnant women were examined sonographically in the second trimester to evaluate the prevalence of fetal lateral ventricle choroid plexus cysts and the incidence of ultrasonographic anomalies associated with such cysts in fetuses with trisomy 18 referred from cytogenetic laboratories. Thirty cases of fetal lateral ventricle choroid plexus cysts (0.6%) were detected during the study period; 28 newborns were normal and two had trisomy 18. One of the affected infants had other associated ultrasonographic abnormalities suggesting aneuploidy, whereas no detectable abnormalities could be found in the other. Three other pregnant women were referred to us from the cytogenetics services because fetal karyotype revealed trisomy 18; in all three cases lateral ventricle choroid plexus cysts and other sonographic abnormalities were observed. In total, we scanned five fetuses with trisomy 18, of which all had lateral ventricle choroid plexus cysts and four had associated detectable anomalies. We could not find any association between cyst size, number, or laterality and trisomy 18. In addition to the five cases of trisomy 18 described, we found 33 other fetuses reported with trisomy 18 in the second trimester; of this total, 25 (66%) had lateral ventricle choroid plexus cysts and 30% had no other detectable abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)