前期研究和文献证实：利用孕妇外周血游离胎儿DNA进行无创性产前诊断安全可行,但易受高母体背景的干扰，本研究提出假设，能否将母体循环中胎儿miRNA作为分子标签，摆脱其母体背景的干扰，建立miRNA表达谱并探讨其分布特征与功能。为出生缺陷的早期预警和个体化诊断提供线索。本研究拟以孕妇外周血中胎儿遗传信息为靶标，结合和发展高通量测序和生物信息学分析技术，开展从基础到临床，临床到基础两个方向的研究，将母体循环中miRNA与高通量测序研究有机结合起来。构建 DS 胎儿全基因组 miRNA 表达谱；并利用生物信息学技术分析其染色体分布特征和异常表达 miRNA 与 DS 各性状的关联，为 DS 胎儿的无创性产前诊断和个体化干预提供佐证；为进一步探索 21号染色体编码 miRNA 的功能提供新的研究靶点。

To explore the expression profile characteristics of fetal miRNAs as molecular target from maternal circulation during the development of Down syndrom （DS） fetuses and to identify if other new miRNA genes reside in the human chromosome 21. DS and matched control fetal cord blood mononuclear cells samples verified by chromosome karyotype were collected. Total RNA was extracted and equally pooled to construct the small RNA cDNA sequencing library of DS and control group, respectively. And then, the Illumina Solexa high-throughput nucleotide sequencing technology was performed. The results were analyzed with bioinformatics analysis software and validated by stem-loop RT-PCR with the remaining samples. It is showed that the DS fetal mononuclear cells have its own specific miRNA expression profile and chromosome distribution characteristics. Abnormally expressed miRNAs may be involved in the birth deficiency of DS fetus, Moreover, the significantly dysregulated and specifically expressed fetal miRNAs are potential non-prenatal diagnosis biomarkers for DS fetus personalized diagnosis.