Genetic amniocentesis is indicated in cases with isolated choroid plexus cysts

OBJECTIVE: To determine whether isolated choroid plexus cysts (CPC) are associated with increased risk of chromosome defects and to ascertain whether cyst characteristics affect the risk of an abnormality. STUDY DESIGN: In a multicenter prospective study, targeted ultrasound, including a search for structural defects, was performed on midtrimester fetuses (13-24 weeks) found to have CPC. The largest cyst diameter and locularity were recorded in the majority of cases. Neonatal or pédiatrie outcomes were ascertained in the non-amniocentesis cases by contacting the parent, referring obstetrician or by pédiatrie chart review. The study group consisted of cases with isolated CPC and with fetal karyotype or with pédiatrie follow up information in pregnancies not undergoing genetic amniocentesis. RESULTS: There were 710 cases of CPC, 35 (4.9%) of which had structural defects. Of 675 cases of isolated CPC', 565 (78.5%) had amniocentesis. In the study group there were 3 cases of Trisomy 21,2 trisorm 18, one case each with 48, XXYY, 69, XXV, 46, XX, del (6q) and along with 3 mosaic (trisomy 22, and 2 sex chromosome) abnormalities. The risk of abnormal karyotype was 11/675 [1/61]. The risk in women at low risk for aneuploidy based on maternal age (i.e. <35 years) was 6/452 ( 1/75). There was no significant difference in the rates of chromosome defects in unilocular vs multilocular cysts (10/284 vs 5/200, p = 0.5), or in cyst diameter of abnormal vs normal cases (9.9 vs 7.9 mm, p = 0.33) CONCLUSION: Isolated choroid plexus cysts were associated with an elevated risk of chromosome defects most of which are non-trisomy 18 cases. The risk is also elevated among women <35 years. Cyst characteristics such as size and locularity do not predict aneuploidy risk. These findings indicate that there is a high risk of chromosome defects in isolated CPC and justifies a recommendation of amniocentesis even in cases with othenvise normal appearing fetal anatomy.