Application of Next Generation Sequencing in Noninvasive Prenatal Genetic Diagnosis

Presently, common invasive testing methods include chorionic villus sampling (CVS), amniocentesis and percutaneous umbilical blood sampling. These procedures produce a prenatal genetic diagnosis with 99 per cent accuracy. However, depending on the hospital and experience of the physician, they also generate a 1 per cent chance of miscarriage. NIPD, if accurate and efficient, is considered the 'Holy Grail' of prenatal genetic diagnosis, and with time is expected to replace invasive testing. The road to improve NIPD to achieve similar results to invasive techniques has been long and arduous. Initially, several methods for non-invasive prenatal screening of frequently encountered trisomy syndromes were developed that relied on the examination of multiple biochemical markers in maternal blood during the second trimester of pregnancy. Methods to detect Down syndrome in the first trimester were also developed, which were based on foetal ultrasound features combined with maternal serum assessment of biochemical markers. Although these methods did not carry a risk of miscarriage, they were only accurate 50 to 80 per cent of the time, with a high degree of false positive and false negative results.