Objective: To explore the possibility of non-invasive prenatal diagnosis of Down syndrome by dual color fluorescence in situ hybridization with co-denaturation.
Methods: Fetal nucleated red blood cells labeled by anti-glycophorin a monoclonal immunomagnetic microbeads were enriched from maternal peripheral blood by magnetic activated cell sorting. The ploidy of chromosome 21 and sex of fetuses were determined using two-color fluorescence in situ hybridization with 21 and Y chromosome probes denatured by codenaturation. The accuracy of prediction was verified according to the karyotype of fetuses by analysis of amniotic cells.
Results: The ploidy of chromosome 21 of fetuses from 11 pregnant women was predicted normal. The results were correctly identified by the fetal karyotypes. 5 pregnant women were predicted carrying male fetuses. The number and mean number of male fetal nucleated red blood cells were 9-65 and 25 per 2 ml, respectively. The purity of male fetal erythrocytes enriched from maternal peripheral blood was 1.4%-18.8%; 6 pregnant women were predicted carrying female fetuses, and no male fetal nucleated red blood cell was found. The results of sex prediction were consistent with the kayotypes of fetuses by analysis of amniotic cells.
Conclusion: It is possible to predict the ploidy of chromosome 21 and the sex of fetuses when fetal nucleated erythrocytes enriched by direct immunomagnetic labeling followed by magnetic activated cell sorting are analyzed using two-color fluorescence in situ hybridization with Y and 21 chromosome probes through codenaturation.