Detection of cell-free fetal DNA in maternal serum for a new prenatal screening marker of Down's syndrome

Objective Detection of cell-free fetal DNA in maternal serum by TaqMan probe real-time quantitative polymerase chain reaction(real-time quantitative PCR) and on the basis of it's amount to discuss the feasibility as a new prenatal screening indicator of Down's syndrome.Methods Cell-free fetal DNA in maternal serum was isolated from 42 samples in the midtrimester(16～19w) pregnancy.Samples consisted of 7 women carrying male trisomy 21 fetuses,18 carrying euploid male fetuses,and 17 carrying female fetuses.TaqMan probe real-time quantitative PCR was used to detect both DYS14 gene on Y chromosome and β-actin gene of the mothers and the fetuses.Results Abnormal high concentrations of cell-free fetal DNA were found in a proportion of women carrying male trisomy 21 fetuses.Mean serum fetal DNA concentrations were 94.5 genomic equivalents(GE)/ml for Down's syndrome cases and 42.8 GE/ml for the euploid controls(P0.01).(Down's) syndrome pregnancies exhibit 2.2-hold higher levels of maternal serum cell-free fetal DNA compared with matched controls.None of the samples from women carrying female fetuses had detectable Y-chromosomal signals.Conclusion Cell-free fetal DNA in maternal serum is a potential prenatal screening maker for trisomy 21.