EVIDENCE OF A 2ND GAMETE FUSION AFTER THE 1ST CLEAVAGE OF THE ZYGOTE IN A 47-XX+18/70-XXX+18-MOSAIC - A REMARKABLE DIPLOID TRIPLOID DISCREPANCY AFTER CVS

A 70,XXX, + 18 karyotype was found by chorionic villus sampling, while the fetal fibroblast culture of the affected fetus revealed a 47,XX, + 18 karyotype. From several possible mechanisms, we assume that a second gamete fusion occurred after the first cell division of the zygote. According to this interpretation, the mosaicism arose in very early pregnancy (at the two-cell stage). This discrepancy can therefore be explained by selection pressure, due to the differentiation processes in the embryonic tissues.