Figure 1. Detecting Down syndrome. Papageorgiou et al. have devised a method for noninvasive, prenatal detection of trisomy 21, the chromosomal abnormality that underlies Down syndrome.

A blood sample from a pregnant woman [a] contains mostly her DNA but also trace amounts of fetal DNA, which is hypermethylated (Me) compared with the mother's DNA. The amount of fetal DNA in the sample is increased by immunoprecipitation with a mAb that recognizes methylated DNA [b]. The DNA is then amplified and analyzed by real-time quantitative PCR [c]. Because of the extra chromosome, the yield of amplified DNA is higher from women carrying a fetus with trisomy 21 than from women with genetically normal fetuses.

The technology has been licensed to NIPD Genetics Ltd., a new company that is developing noninvasive, prenatal diagnostics for Down syndrome and other chromosomal abnormalities. Sequenom Inc. and Artemis Health Inc. are developing DNA sequencing-based diagnostic technologies to detect Down syndrome.