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The current mainstream clinical prenatal examinations employ invasive sampling approaches to extract the fetal genetic material, including the commonlu used Amniocentesis and Chorionic Villi Sampling(CVS) (Fig.1). This is followed by immunohistochemistry, PCR, Fluorescence In Situ Hybridization(FISH) or other methods for the analysis on the tiny amount of genetic material obtained. Themajor downside of this approach is the significant increased rate of miscarriage. For instance, in a published study consisting of 4606 cases, the risk of miscarriage was significantly increased by 1% after using amniocentesis compared with controls.

Fig. 1:Existing method of prenatal diagnosis
AmniocentesisUltrasonic examinationChorionic Villi Sampling

Therefore the pregnant women often end up in a dilemma of whether taking these invasive examining approaches or not. Non-invasive approach is an inevitable trend for future prenatal diagnosis. Another major problem of the invasive testing approaches lies in the low sensitivity and accuracy, requiring a large quantity of genetic material from the fetus to perform various tests before reaching the final diagnosis.

There exist two sources of non-invasive fetal genetic material, including cell-free fetal DNA(cffDNA) and nucleated red blood cell (NRBC) circulating in the mother’s blood (Fig.2).

Fig. 2:Non-invasive fetal genetic material in mother’s blood

The current commercialized non-invasive prenatal examinations rely on cffDNA to perform tests on a few genetic diseases, especially on chromosome diseases (e.g. Down Syndrome, an additional copy of Chromosome 21) after limited sequencing or PCR amplification. However, the majority of cffDNA originated from the mother, with only a limited amount from the fetus (3.4% ~ 6.2%) existing as short and incomplete DNA segments. Therefore, such fetal DNA source can only provide very limited genetic information of the fetus. In addition, the accuracy of the final diagnosis can be unreliable due to the uncertainty of existing algorithm. For example, in a pilot study consisting of 753 cases with Down Syndrome possibility, only 79.1% of them were identified by the cffDNA-based approach. Finally, in order to obtain more genetic information from cffDNA, the cost and complexity of the testing will increase dramatically, not to mention the needs of the genetic information from both parents, which seems impractical at the current stage.

In order to gain the full genetic information of the fetus using a non-invasive sampling approach, the only feasible approach is to isolate fetal cells in completeness from the maternal blood. Hence we have been committed to develop a non-invasive technique isolating free fetal cells and their molecular diagnosis.

At present, we have already established groundbreaking method for the isolation of nucleated fetal cell. We are able to isolate fetal cell from 10~20cc maternal blood at a stage as early as 10 to 12 weeks of pregnancy. Due to the limited quantity of cells (10 to 100), we have further developed a customized whole-genome and trancriptome sequencing technologies that can capture the complete genetic information of the fetus from under 10 cells, and the sequencing results can be used for downstream clinical diagnosis. In contrast to other current non-invasive prenatal diagnosis approaches focusing on a few chromosome diseases, 3500 genetic mutations associated with genetic disorders can be tested using our product, providing the latest, the most accurate and the most comprehensive prenatal testing based on our own bioinformatics platform.