title: Second trimester choroid plexus cysts and trisomy 18.
abstract: OBJECTIVE
  In this study, the aims were to reveal the incidence of isolated choroid plexus cyst in our population, and to discuss the accuracy of distinguishing either an isolated or non-isolated choroid plexus cyst.
  
  
  METHODS
  The study population was consisted of 10594 pregnant women. The patients with choroid plexus cysts were classified into two groups: isolated and non-isolated. Detailed ultrasonographic examination and genetic counseling were performed and triple screening test was ordered. The incidence, sensitivity, specificity, false-positive rate and likelihood ratio of cases with isolated choroid plexus cyst for trisomy 18 were determined.
  
  
  RESULTS
  Choroid plexus cysts were identified in 109 patients (109/10594; 1.02%). In 102 patients isolated choroid plexus cysts, and in seven patients additional fetal anomalies supporting trisomy 18 were detected. Trisomy 18 was detected in four patients, and one of them had isolated choroid plexus cyst. The likelihood ratio in cases of isolated choroid plexus cysts for trisomy 18 was 9.51 (95% confidence interval, 0.2-41).
  
  
  CONCLUSIONS
  According to the study the individual risk for trisomy 18 in isolated choroid plexus cyst should be calculated by using the likelihood ratio. These data allows the physician to express the individual risk of trisomy 18 and permits more accurate genetic counseling.
authors.affiliation: Department of Perinatology, Zeynep Kamil Women and Children Hospital, Uskudar, Istanbul, Turkey. zekisa@ixir.com
authors.forename: Z
authors.initials: Z
authors.lastname: Sahinoglu
authors.forename: M
authors.initials: M
authors.lastname: Uludogan
authors.forename: C
authors.initials: C
authors.lastname: Sayar
authors.forename: B
authors.initials: B
authors.lastname: Turkover
authors.forename: G
authors.initials: G
authors.lastname: Toksoy
mesh_terms: D001927:Brain Diseases / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000235:genetics*; D002831:Choroid Plexus / Q000000981:diagnostic imaging*; D002887:Chromosomes, Human, Pair 18; D003560:Cysts / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000235:genetics*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis; D011446:Prospective Studies; D014314:Trisomy; D014421:Turkey / Q000453:epidemiology; D014463:Ultrasonography