Follow-up investigations in uncultured amniotic fluid cells after uncertain cytogenetic results

Fluorescence in situ hybridization (FISH) on uncultured amniotic fluid (AF) cells is a widespread technique for the rapid prenatal detection of specif ic chromosome aberrations. During a 6-year period (1993-1998) we used FISH for quick follow-up investigations in uncultured AF cells after finding an uncertain chromosome aberration in a first chorionic villus (CV) or AF samp le in 79 cases. These FISH results were compared with conventional cytogene tic results of the AF cell cultures in all cases. We found discrepant FISH and cytogenetic results in four instances. In general, FISH on uncultured A F cells proved to be a reliable technique for the rapid differentiation bet ween confined placental mosaicism and true fetal mosaicism, and between pse udomosaicism and true mosaicism, respectively. Uncultured cells may sometim es even better reflect chromosomal mosaicism than cultured cells, since the y are not subject to culture induced selection mechanisms. However, we foun d evidence that exceptional cases of tissue confined mosaicism may go undet ected in uncultured cells. Copyright (C) 2001 John Wiley & Sons, Ltd.