[Distinctive features of euploid-aneuploid mosaicisms diagnosed by amniocentesis (author's transl)].

Although infrequent, mosaicism in amniotic fluid may lead to a questionable diagnosis. From a personal case and a general review of the literature the authors conclude that euploid-aneuploid mosaicism must be strongly considered as real if it is expressed in more than one clone, in more than one flask, if it is confirmed by a second amniocentesis and if the abnormal cell line is caused by the loss or acquisition of a chromosome compatible with a known pattern or syndrome. Other patterns documented in such a material have to be considered on their own merits as they may or may not be confirmed after birth.