Non-invasive prenatal diagnosis of a microdeletion

14 November 2011

An example of the use of non-invasive prenatal diagnosis (NIPD) for the identification of a chromosomal microdeletion has been published in the New England Journal of Medicine.
NIPD, the brainchild of Professor Dennis Lo, has a range of current and potential applications, including for the identification of fetal sex and RhD-status, and the presence of selected genetic and chromosomal abnormalities. The first commercial tests for trisomy 21 (Down’s Syndrome) recently went on sale in the US (see previous news).
The technique has limitations, but the new report details a single example of the identification of a fetal 4-Mb deletion on chromosome 12 using a maternal blood sample taken at 35 weeks. The microdeletion, inherited from the father and observed in an older child of the couple with developmental delay, had been previously diagnosed using the standard invasive techniques of amniocentesis and array-based comparative genomic hybridization.

Comment: Although this is an isolated case of a diagnosis performed late in pregnancy, it is a valuable example of how NIPD might in theory be employed earlier to diagnose familial much smaller chromosomal abnormalities than aneuploidies. Couples could then obtain this information without risk to the pregnancy, and with more time to make a decision about whether or not to proceed with an affected pregnancy.