Abstract: A method for the identification of human foetal cell nuclei is provided wherein the method involves subjecting chromosomes of cell nuclei to exonucleolytic digestion by an enzyme so as to remove end regions of each chromosome; and detecting the presence of a DNA sequence remaining in foetal DNA but absent from maternal DNA as a result of the digestion process. Once identified, the foetal DNA can be subject to diagnosis for example to detect chromosomal abnormalities.