Examination of Fetal Sex in the Peripheral Blood of Pregnant Women before 9 Completed Weeks, Gestation

Abstract

Objective To investigate the feasibility of using fetal cells and free DNA in maternal blood for non-invasive prenatal diagnosis. Methods 150 pregnant women were studied at 5 ～ 9 completed weeks' gestation. Fetal cells were isolated using lymphocyte separation liquid and 3% gelatin. Furthermore, fluorescence in situ hybridization (FISH) was used to examine the terminal of Y chromosome. Nested polymerase chain reaction (PCR) and real-time fluorescence quantitative PCR(FQ-PCR) were used to amplify the SRY gene of the plasma DNA extracted from the same 150 samples of maternal blood. Results The sensitivity of FISH, nested PCR and FQ-PCR was 73.2%, 78% and 85.4%, respectively. The specificity of the FISH, nested PCR and FQ-PCR was 96.2%, 100% and 100%, respectively. Using FISH, we could find male fetal cells in maternal blood as early as the 49th day. We could also find fetal free DNA in maternal plasma as early as the 49th and the 42nd day in pregnancy using nested PCR and FQ-PCR. Conclusion All of the three methods are valuable for non-invasive prenatal diagnosis. Among them FQ-PCR is the best because we can examine fetal DNA earlier by using it. Key words: Prenatal diagnosis; Fetal cells; Fetal DNA; FISH; Nested PCR; FQ-PCR