Rapid identification of a small dicentric supernumerary marker derived from chromosome 16 with a modified FISH technique on amniotic fluid

Small supernumerary marker chromosomes are seldom found in prenatal diagnos is and the majority of them are difficult to identify. The only possibility to give a more precise prognosis is by establishing its origin. FISH is th e best technique to identify the chromosomal origin, but in the majority of cases large amounts of chromosomal material are needed and this is time co nsuming. We have used a modification of the FISH technique that allows the hybridization of several probes on one slide. Using this method, we have id entified the first de novo mosaic dicentric supernumerary marker derived fr om chromosome 16 (smaller than chromosome 21) in amniotic fluid. The gestat ion and the follow-up of the baby were normal. Copyright (C) 2000 John Wile y & Sons, Ltd.