Detection of fetal cells with common chromosomal aneuploidies in maternal blood.

This study was designed to address the feasibility of detection of fetal cells with chromosome abnormalities in maternal blood. Peripheral venous blood samples were collected from 150 pregnant women 1 day to 8 weeks before invasive examinations (amniocentesis, chorionic villus sampling, or fetal blood sampling). Fetal nucleated red blood cells were isolated by using a triple-density gradient followed by magnetic-activated cell sorting to select CD71 cells. Fluorescence in situ hybridization (FISH) with probes specific for chromosomes X, Y, 13, 18, and 21 was used to detect fetal cells from aneuploid pregnancies. The hybridization efficiency was greater than 98% for each probe in normal controls, and approximately 20% of all cells failed to hybridize after magnetic-activated cell sorting. Of the 10 aneuploid pregnancies identified with invasive procedures, trisomic fetal cells were identified 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 fetal cells could be successfully detected in eight of 10 patients in the current study, the existence of some limiting factors, such as scarcity of fetal cells and poor hybridization efficiency of FISH, raises questions about its clinical suitability for routine use.