Prenatal detection of fetal Down's syndrome from maternal plasma

Fetal DNA is present in maternal plasma, and a proportion of such DNA is se en in intact fetal cells. We investigated the use of fluorescence in-situ h ybridisation (FISH) techniques on maternal plasma samples, in plasma sample s obtained from three women carrying fetuses affected by trisomy 21 (Down's syndrome), we identified fetal cells with three chromosome-21 signals. The se results show the feasibility of non-invasive detection of fetal chromoso mal aneuploidy by maternal plasma analysis.