Approximately half of the erythroblasts in maternal blood are of fetal origin

The enrichment of fetal erythroblasts from the peripheral blood of pregnant women is currently actively pursued for the development of a non-invasive means of prenatal diagnosis. Since erythroblasts in maternal blood are not all of fetal origin, and currently no reliable method exists to distinguish between the maternal and fetal erythroblasts, their use for prenatal diagn osis is not without uncertainty. The purpose of this study was to determine the percentage of fetal erythroblasts in maternal blood at the single cell level and to what extent such cells can reproducibly be used for polymeras e chain reaction (PCR)-based prenatal diagnostic analyses. Erythroblasts we re enriched from the peripheral blood of rhesus negative pregnant women usi ng magnetic cell sorting (MACS). Single erythroblasts identified morphologi cally were individually micro-manipulated and analysed by a multiplex PCR r eaction for the fetal SRY and rhesus D genes. As a control for the PCR reac tion the beta-globin gene was used. The PCR results were validated by the r esults obtained by invasive procedures. In all instances where single eryth roblasts were examined, the correct fetal genotype for the two fetal specif ic loci was detected. Furthermore, our results indicate that similar to 50% of the enriched erythroblasts are of fetal origin.