Fetal cells in cervical mucus and maternal blood.
Research in developing effective and accurate methods for non-invasive prenatal diagnosis has focused on two main techniques: the retrieval of trophoblast cells from the cervix and the enrichment of fetal erythroblasts from the blood of pregnant women. The isolation of fetal cells by both approaches has permitted the identification of fetal aneuploidies by the use of fluorescence in-situ hybridization (FISH) with appropriate probes, as well as fetal single gene disorders by polymerase chain reaction (PCR). In the latter instance, it has been shown that in order to attain the high degree of specificity required for prenatal diagnosis, it is necessary to analyse single fetal cells isolated by micromanipulation. This practice has permitted the successful characterization of fetal rhesus status, haemoglobinopathies, Duchenné's muscular dystrophy and spinal muscular atrophy, amongst others.Further developments include investigations into whether the diagnostic potential of fetal cells retrieved by either method can be expanded by the possible culturing of such cells, as well as the possibility of performing successive rounds of FISH and PCR by the recycling of isolated fetal cells.A novel observation that our group has made is that the traffic of fetal cells is enhanced in pregnancies affected by the pregnancy related disorder, pre-eclampsia. Our subsequent investigations have shown that this elevation in fetal cell traffic may serve as an early marker for those pregnancies at risk for this disorder.A very recent exciting discovery has been that free extracellular fetal DNA can be detected in the plasma and serum of pregnant women, which may permit the rapid and accurate detection of uniquely fetal loci, such as the fetal rhesus D gene in rhesus D negative pregnant women.