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 FQ-PCR 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 .