Quantitative analysis of fetal cell-free DNA in maternal plasma at early pregnant stage

Objective:A mean concentration was shown by quantitative analysis of fetal cell-free DNA in maternal plasma.Methods:Fetal DNA in maternal plasma was isolated from 50 samples(range,7-9weeks).Fetal DNA in maternal plasma was measured using real-time fluorescence quantitative polymerase chain reaction(FQ-PCR) for the SRY gene on the Y chromosome.Results:38 women at early pregnant stage(range,7-9weeks) carried male fetuses,32 samples of them were positive.The mean concentrations in women carrying male fetuses were(149.25±1.96×59.17) copies/ml.The median fetal DNA levels were 149.1 copies/ml.The results of FQPCR were negative in the 12 women who carried female fetuses.Conclusions The results show that fetal SRY gene can be found at early pregnant stage in maternal plasma by the use of FQ-PCR.The specificity of the system reaches 100% and the sensitivity 84.21%.Quantitative analysis of fetal cell-free DNA in maternal plasma is of great value in the non-invasive prenatal diagnosis.