Prenatal diagnosis of trisomy 20 mosaicism indicating an extra embryonic origin

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.