New prospects for non- invasive prenatal dıagnosıs

Three steps appear essentia! ıo allow non-invasive prenata! diagnosis: !) distinguishing feta! from maternal eells, 2) emiehment of the feta! eell popu!ation, and 3) use of rapid methods of analysis on smail number of feta! cells or DNA, respeetive!y. To identify fetal eells severa! monodona! antibodies are used, buı this is still problemaıle. Furthermore, the number of feta! eells in the maternal circu!ation is searce; in the order of 10-5 to 10-6 or less. Therejore emlehment strategies usingk se!eetive density gradients, magnetic ceU sorting (MAeS) or fluoreseent activated ceıı sorting (FAeS) are required. Rapid analysis can be actueved by tests based on polymerase chain reaction (peR) Ol' fluorescent in situ hybridisation (FISH). Using these techniques, feta! sexing and fetal aneuploides have been diag~ nosed in fetal cells recovered from maternal blood, and the diagnoses have been conrirmed by eonventional invasive methods. Thus, the prospects for non~invasive prenatal diagnosis are promising. However fast and better cell separation techniques are still needed a!ong with further improvements of deteetion methods. Other major issues to be addressed in the future include the investigation of the presenee and frequency of fetal eells in maternal blood throughout gestation, whether there are differences in individual pregnancies, and the persistence and duration of feta! cells in maternal blood after delivery,