Editing Choroid plexus (section)

===Choroid plexus cysts===
{{Main|Choroid plexus cysts}}
{{See also|Triple test}}
During [[fetal development]], some [[choroid plexus cysts]] may form. These fluid-filled cysts can be detected by a detailed [[Obstetric ultrasonography#Second and third trimester|second trimester ultrasound]]. The finding is relatively common, with a prevalence of ~1%. Choroid plexus cysts are usually an isolated finding.<ref name="pmid10607945" /> The cysts typically disappear later during pregnancy, and are usually harmless. They have no effect on infant and early childhood development.<ref name="pmid9241291">{{cite journal | vauthors = Digiovanni LM, Quinlan MP, Verp MS | s2cid = 40130437 | title = Choroid plexus cysts: infant and early childhood developmental outcome | journal = Obstetrics and Gynecology | volume = 90 | issue = 2 | pages = 191–4 | date = August 1997 | pmid = 9241291 | doi = 10.1016/S0029-7844(97)00251-2 }}</ref>

Choroid plexus cysts are associated with a 1% risk of fetal [[aneuploidy]].<ref name="pmid9678699">{{cite journal | vauthors = Peleg D, Yankowitz J | title = Choroid plexus cysts and aneuploidy | journal = Journal of Medical Genetics | volume = 35 | issue = 7 | pages = 554–7 | date = July 1998 | pmid = 9678699 | pmc = 1051365 | doi =  10.1136/jmg.35.7.554}}</ref> The risk of aneuploidy increases to 10.5-12% if other risk factors or ultrasound findings are noted. Size, location, disappearance or progression, and whether the cysts are found on both sides or not do not affect the risk of aneuploidy. 44-50% of [[Edwards syndrome]] (trisomy 18) cases will present with choroid plexus cysts, as well 1.4% of [[Down syndrome]] (trisomy 21) cases.  ~75% of abnormal karyotypes associated with choroid plexus cysts are trisomy 18, while the remainder are trisomy 21.<ref name="pmid10607945">{{cite journal | vauthors = Drugan A, Johnson MP, Evans MI | title = Ultrasound screening for fetal chromosome anomalies | journal = American Journal of Medical Genetics | volume = 90 | issue = 2 | pages = 98–107 | date = January 2000 | pmid = 10607945 | doi =  10.1002/(SICI)1096-8628(20000117)90:2<98::AID-AJMG2>3.0.CO;2-H}}</ref>