Gerovassili Ageliki, Garner Chad, Nicolaides Kypros H, Thein Swee Lay, Rees David C
Division of Gene and Cell Based Therapy, King's College London School of Medicine, London, UK.
Prenat Diagn. 2007 Feb;27(2):104-10. doi: 10.1002/pd.1607.
Previous studies on the association of fetal cell-free (cf)DNA levels in maternal circulation have produced conflicting results but the sample sizes were small and based on archived material. We aimed to quantify the levels of fetal and total cfDNA on prospectively collected samples, to understand their correlation with other variables and to clarify their diagnostic value.
DNA from pre-CVS maternal plasma was extracted from 264 controls, 72 trisomy 21, 24 trisomy 18, 12 trisomy 13, 16 Turner's syndrome and 8 triploidy first-trimester pregnancies and quantified using real-time PCR. beta-globin was used to determine total cfDNA levels and DYS14 and SRY assays to determine fetal cfDNA levels.
Fetal cfDNA levels (DYS14) showed correlation with crown rump length (CRL) (p = 0.004), BMI (p = 0.01) and storage time (p = 0.007) while there was an inverse correlation of total cfDNA levels with nuchal translucency (NT) (p = 0.001). No significant difference was observed between the levels of fetal cfDNA in controls and aneuploidy cases.
Quantification of fetal and total cfDNA in maternal circulation showed inverse correlation between NT and total cfDNA levels. Our results also suggest that fetal cfDNA is not an ideal prognostic marker for chromosomal abnormalities in first-trimester pregnancies.
以往关于母血中胎儿游离（cf）DNA水平相关性的研究结果相互矛盾，且样本量小，基于存档材料。我们旨在对前瞻性收集的样本中的胎儿和总cfDNA水平进行定量，了解它们与其他变量的相关性，并阐明其诊断价值。
从264例对照、72例21三体、24例18三体、12例13三体、16例特纳综合征和8例三倍体孕早期妊娠的绒毛取样前母血血浆中提取DNA，采用实时荧光定量PCR进行定量分析。使用β-珠蛋白测定总cfDNA水平，使用DYS14和SRY检测法测定胎儿cfDNA水平。
胎儿cfDNA水平（DYS14）与顶臀长（CRL）（p = 0.004）、体重指数（BMI）（p = 0.01）和储存时间（p = 0.007）呈正相关，而总cfDNA水平与颈项透明层（NT）呈负相关（p = 0.001）。对照和非整倍体病例的胎儿cfDNA水平无显著差异。
母血中胎儿和总cfDNA的定量分析显示NT与总cfDNA水平呈负相关。我们的结果还表明，胎儿cfDNA不是孕早期染色体异常的理想预后标志物。
