ISOLATING FETAL CELLS IN THE MATERNAL CIRCULATION

Fetal cells exist in maternal blood and can be utilized for prenatal g enetic diagnosis, The use of polymerase chain reaction (PCR) technolog y on maternal blood has enabled the detection of fetal sex, Mendelian disorders (e.g. beta-globin mutations), HLA polymorphisms and fetal Rh esus (D) blood type, Enrichment for erythroblasts and trophoblasts by various density gradient and now sorting techniques followed by fluore scence in-situ hybridization (FISH) with chromosome-specific DNA probe s has allowed detection of trisomy 21, trisomy 18, Klinefelter syndrom e (47,XXY) and 47,XYY, The fetal cell type that has generated the most success is the nucleated erythrocyte; however, trophoblasts, lymphocy tes and granulocytes are also considered to be present in maternal blo od. Fetal cells circulate in maternal blood during the first and secon d trimesters,,with frequency increasing as gestation advances, Emphasi s is thus now directed toward determining the most practical and effic acious manner for this technique to be applied to prenatal genetic dia gnosis, A large scale collaboration of clinical evaluations is underwa y in the USA, upon completion of which assessment can be made of wheth er this technology can serve as an alternative to conventional invasiv e and non-invasive methods of prenatal cytogenetic diagnosis.