Editing Down syndrome (section)

====Invasive genetic testing====
Amniocentesis and chorionic villus sampling are more reliable tests, but they increase the risk of [[miscarriage]] by between 0.5–1%.<ref name=Tab2010>{{cite journal | vauthors = Tabor A, Alfirevic Z | title = Update on procedure-related risks for prenatal diagnosis techniques | journal = Fetal Diagnosis and Therapy | volume = 27 | issue = 1 | pages = 1–7 | year = 2010 | pmid = 20051662 | doi = 10.1159/000271995 | doi-access = free | oclc = 23338607 }}</ref> The risk of limb problems may be increased in the offspring if chorionic villus sampling is performed before 10 weeks.<ref name=Tab2010/> 
[[File:Prenatal Down syndrome screening algorithm.png|thumb|An example of an algorithm for determining the indication for prenatal genetic testing of Down syndrome<ref>{{cite web|url=https://www.uptodate.com/contents/should-i-have-a-screening-test-for-down-syndrome-during-pregnancy-beyond-the-basics/print|title=Patient education: Should I have a screening test for Down syndrome during pregnancy? (Beyond the Basics)|website=UpToDate| vauthors = Halliday JV, Messerlian GM, Palomaki GE }}</ref>]]
The risk from the procedure is greater the earlier it is performed, thus amniocentesis is not recommended before 15 weeks gestational age and chorionic villus sampling before 10 weeks gestational age.<ref name=Tab2010/>