Noninvasive prenatal testing by maternal plasma DNA analysis: current practice and future applications.

Prenatal screening of fetal chromosomal aneuploidies and some common genetic diseases is an integral part of antenatal care. Definitive prenatal diagnosis is conventionally achieved by the sampling of fetal genetic material by amniocentesis or chorionic villus sampling. Due to the invasiveness of those procedures, they are associated with a 1 in 200 chance of fetal miscarriage. Hence, researchers have been exploring noninvasive ways to sample fetal genetic material. The presence of cell-free DNA released by the fetus into the circulation of its mother was demonstrated in 1997. Circulating fetal DNA is therefore obtainable through the collection of a blood sample from the pregnant woman without posing any physical harm to the fetus. By analyzing this source of fetal genetic material, researchers have succeeded in developing DNA-based noninvasive tests for the assessment of Down syndrome and single gene diseases. Since the end of 2011, tests for the noninvasive assessment of chromosomal aneuploidies have become commercially available in parts of the world. Recommendations from professional groups have since been made regarding how these tests could be incorporated into the framework of existing prenatal screening programs. More recently, cell-free circulating fetal DNA analysis have been shown to be applicable to the deciphering of the fetal molecular karyotype, genome and methylome. It is envisioned that an increasing number of the noninvasive prenatal tests will become clinically available. The ethical, social and legal implications of the introduction of some of these tests would need to be discussed in the context of different cultures, societal values and the legal framework.