Enrichment of fetal nucleated red blood cells from the maternal circulation for prenatal diagnosis:: Experiences with triple density gradient and MACS based on more than 600 cases

Objective: We wanted to obtain statistically relevant data about the efficiency of our method for the isolation of fetal nucleated red blood cells (NRBCs) from the maternal circulation. Methods: More than 600 samples were investigated using a triple density gradient followed by magnetic separation of anti-CD71-labeled cells, and yields and purities of recovered NRBCs were determined. Results: The enrichment effectivity as well as the morphological condition of cells was reproducibly good, if blood samples were enriched within 48 h after sampling. The efficacy was independent of various methodological parameters and our technique was superior to other magnetic cell-sorting techniques. Mean yields and purities of NRBCs increased with increasing gestational age, ranging from 100 to 1,000 cells per 40-ml blood sample and from 0.1 to 1%, respectively, from the 6th week of gestation to term. In pregnancies with preeclampsia NRBCs were increased by a factor of 10. Conclusion: Our enrichment technique proved to be optimized with respect to various methodological parameters, which were compared in the present study, and it is efficient and reproducible for the enrichment of NRBCs from the maternal circulation in all three gestational trimesters.