PRENATAL-DIAGNOSIS OF TRISOMY-13 ON FETAL CELLS OBTAINED FROM MATERNAL BLOOD AFTER MINOR ENRICHMENT

In a pilot study to establish fetal nucleated red blood cell (NRBC) de tection in maternal blood, trisomy 13 was diagnosed by FISH analysis a t 11 weeks' gestation. The NRBCs were detected after a single-step fic oll density gradient enrichment. In blood samples taken both before an d after CVS, 52 and 80 NRBCs, respectively, were found to be positive for fetal haemoglobin. In 47 per cent of these cells. FISH analysis fo r X and Y chromosomes confirmed the fetal sex. Moreover, 48 per cent o f these NRBCs showed three fluorescent signals for a chromosome 13 pro be, which confirmed the diagnosis of trisomy 13, previously detected a t CVS karyotyping. This is the first report of non-invasive prenatal d iagnosis of trisomy 13, i.e., pre-CVS, in the first trimester. The hig h number of fetal NRBCs detected indicates a connection with aneuploid y, probably due to early impairment of the fete-maternal barrier. (C) 1998 John Wiley & Sons, Ltd.