Detection of fetal cells with common chromosomal aneuploidies in maternal blood

This study was designed to address the feasibility of detection of fetal ce lls with chromosome abnormalities in maternal blood. Peripheral venous bloo d samples were collected from 150 pregnant women 1 day to 8 weeks before in vasive examinations (amniocentesis, chorionic villus sampling, or fetal blo od sampling). Fetal nucleated red blood cells were isolated by using a trip le-density gradient followed by magnetic-activated cell sorting to select C D71 cells. Fluorescence in situ hybridization (FISH) with probes specific f or chromosomes X, Y, 13, 18, and 21 was used to detect fetal cells from ane uploid pregnancies. The hybridization efficiency was greater than 98% for e ach probe in normal controls, and approximately 20% of all cells failed to hybridize after magnetic-activated cell sorting. Of the 10 aneuploid pregna ncies identified with invasive procedures, trisomic fetal cells were identi fied in eight. The frequency of fetal cells in the sorted specimens ranged from 0 to 223 per 10,000 maternal nucleated cells. Although the aneuploid f etal cells could be successfully detected in eight of 10 patients in the cu rrent study, the existence of some limiting factors, such as scarcity of fe tal cells and poor hybridization efficiency of FISH, raises questions about its clinical suitability for routine use.