Detection for fetal DNA in maternal plasma by fluorescence quantitative polymerase chain reaction

Objective To investigate the fluorescence quantitative PCR (FQ-PCR) based on TaqMan-MGB( Minor Groove Binder) technique for quantification of fetal DNA in maternal plasma and its variation during pregnancy. Methods Maternal DNA extracted from 237 plasma samples obtained from 30 pregnant women (5-40 gestational weeks and post delivery). The TaqMan-MGB probe and SRY primers were designed to amplify the SRY gene sequence of Y chromosome in maternal plasma by FQ-PCR. Results This system was sensitive enough to detect a male DNA among 20 000 female DNA. Fetal DNA can be detected in maternal plasma as early as 6+6 weeks of gestation and increased with the pregnant progress with the peak level at the third trimester. Between 24- 48 h after delivery, the SRY gene was negative in maternal plasma. The percentage of fetal DNA concentration in maternal total plasma DNA was 4. 88% in the first trimester, 6. 10% in the second and 4. 77% in the third trimester. The SRY positive signal was obtained from samples of 13 women bearing male fetuses and no signal was detected for all of the 17 women bearing female fetuses. Conclusions The FQ-PCR for quantification of fetal DNA in maternal plasma is highly sensitive, specific and reliable. Fetal DNA does present in maternal plasma at a higher concentraton. FQ-PCR may be useful in nonin-vasive prenatal diagnosis.