Down syndrome (trisomy 21), which has an incidence of 1 in 800 live births, is considered to be the most frequent etiology of mental retardation and it is the predominant reason for women seeking prenatal diagnosis [Driscoll & Gross, 2009]. Trisomy 21 is used as a benchmark because it is the most common aneuploidy compatible with life and is associated with mental retardation and serious congen...

the first step in the prenatal diagnosis of x-linked genetic disorders is determining fetus gender. current invasive methods to obtain the dna source of the fetus instead of its miscarriage risk, has harmful stress for high risk pregnancies. cell free fetal dna (cffdna) circulating in the maternal blood, has now become a useful source of noninvasive prenatal diagnosis. considering limitation of...