Non-invasive screening methods of down syndrome through maternal circulation

Down syndrome is the most frequent cause of mental retardation among live births which has shown to be increased in recent years. Efficient and early prenatal screening of this disorder can dramatically decrease the birth rate of it. In this way, various non-invasive screening methods have been introduced that the most successful of them used of free fetal DNA present in maternal circulation. In this regard, various protocols have been introduced which were based on short tandem repeats or polymorphisms and either using techniques as well as digital PCR or mass spectrophotometry. However, among all the performed assays, there are two efficient methods for separation of fetal DNA from total DNA isolated from maternal serum including methods based on sequencing and the different pattern of methylation between fetus and mother that have been seized the most attentions. The present study was aimed to have a brief review on the general types of invasive and non-invasive methods of Down syndrome screening and then the focus was on the details of aforementioned methods in various studies.