Cell-free fetal nucleic acid markers in maternal circulation

Prenatal diagnosis is a critical issue of gynecological practice. To perform a genetic test in this field, it is necessary to obtain placental or fetal material. This material, currently, is achieved through invasive procedures such as chorionic villus sampling or amniocentesis. These invasive procedures carry 1% risk of miscarriage, and other maternal and fetal complications have been reported to relate to these invasive procedures. In 1997, the presence of cell-free fetal DNA (cff-DNA) in the circulation of pregnant women was reported. Fragmented cff-DNA originates primarily from apoptotic syncytiotrophoblasts. It is detectable as early as 18 days following embryo transfer in in vitro fertilization pregnancy and is soon cleared from maternal circulation after delivery, with a mean half-life of 16 min, so it is a suitable source for noninvasive prenatal diagnosis (NIPD) in pregnancy. Following these reports, a new area of research in the diagnostic field was opened however, there are two problems with cff-DNA for the development of the noninvasive diagnostic test, the small proportion of cff-DNA in maternal plasma as little as ~19%, and coexistence with maternal DNA. The presence of cff-DNA in maternal circulation is accepted universally, and although via the discovery of cff-DNA many potentially clinical applications have been assessed such as fetal rhesus D status, sex-linked disorders, monogenic disorders, aneuploidies, and many pregnancy complications such as preeclampsia and preterm labor. But confirming the presence of cff-DNA in maternal plasma extracts is still a challenge in diagnostic tests. Researchers have applied many methods to differentiate the fetal-derived sequences from that of mother. Six identifier markers include Y-specific sequence, polymorphisms, epigenetic difference, DNA size difference, fetal mRNA, and microRNA.

Keywords:

DNA , marker , pregnancy , prenatal diagnosis , RNA