Non-invasive prenatal diagnosis of fetal aneuploidies.

The article focuses on a new concept for non-invasive prenatal diagnosis of aneuploidies by analysis of free fetal DNA circulating in maternal plasma. Free fetal DNA has been successfully used for the determination of fetal sex and rhesus D status on a routine basis by some specialized laboratories. Ravinder Dhallan and colleagues proposed the idea that single-nucleotide polymorphisms (SNPs) could be used to determine the number of fetal chromosomes in maternal blood. Though the approach is not new, the method that Dhallan proposes is. This approach can be used to detect trisomy 21, an aneuploidy that causes Down's syndrome. Details of clinical studies are presented.