IS GENETIC AMNIOCENTESIS WARRANTED WHEN ISOLATED CHOROID-PLEXUS CYSTSARE FOUND

Our aim was to evaluate the prevalence of trisomy Is in the setting of isolated fetal choroid plexus cysts and then to consider the risk of trisomy 18 versus the risks of genetic amniocentesis. Fetuses with cho roid plexus cysts were prospectively obtained from a total mid-trimest er population of 18 861 fetuses with known outcomes. If the fetuses ha d trisomy 18, they were part of the study group and part of the contro l group if they had normal karyotypes. Scans were retrospectively revi ewed for the characterization of cysts according to size, laterality, and appearance (simple or complex echo patterns). Chi-square analysis of contingency tables of results was performed. 208/18 861 (1.1 per ce nt) fetuses had choroid plexus cysts. 201/208 (96.6 per cent) were nor mal fetuses or newborns, while 7/208 (3.4 per cent) of the fetuses wit h choroid plexus cysts had trisomy 18. Overall, 16 fetuses had trisomy 18 and seven (44 per cent) of these had choroid plexus cysts. 0/16 fe tuses had choroid plexus cysts as the only sonographic finding. Althou gh laterality or complexity of the cysts did not correlate with the pr esence or absence of a cytogenetic abnormality, cysts greater than or equal to 10 mm were more often associated with trisomy 18 than with a normal karyotype (P<0.01). We conclude that the discovery of choroid p lexus cysts in otherwise normal fetuses in the late second trimester d oes not by itself justify the risks of genetic amniocentesis.