Prenatal diagnosis of trisomy 20 mosaicism indicating an extra embryonic origin

Abstract
An additional case of amniotic fluid trisomy 20 mosaicism is presented. After careful counselling, the pregnancy continued and a phenotypically normal female was delivered. This case of amniocyte mosaicism establishes the source of aneuploid cell line as amnion. Since an extra‐embryonic origin of the mosaicism has been confirmed, this should be carefully considered as a real possibility in counselling such families.