NIPT需要多大的数据量（reads number）？
调研
2014 Noninvasive prenatal diagnosis of common aneuploidies by semiconductor sequencing 报道 Approximately 65.5% (3.6 million)
2008 Noninvasive diagnosis of fetal aneuploidy by shotgun sequencing DNA from maternal blood 报道 ≈10M raw data，读长25bp ，得到50% unique maping data（5M）
2014 Non-invasive prenatal testing for fetal chromosomal abnormalities by low-coverage whole-genome sequencing of maternal plasma DNA: review of 1982 consecutive cases in a single center 报道 The minimal amount of unique sequencing reads was no less than 3.5 million after alignmen
2012 Noninvasive prenatal detection and selective analysis of cell-free DNA obtained from maternal blood: evaluation for trisomy 21 and trisomy 18
提出 The chromosomal dosage resulting from fetal aneuploidy is directly related to the fraction of fetal cfDNA. For example, a cfDNA sample containing 4% DNA from a T21 fetus should exhibit a 2% increase in the proportion of reads from chromosome 21 (chr21) as compared to a normal fetus. Distinguishing these 2 scenarios with high confidence requires a large number (>93,000) of chr21 observations.
最重要一片文献是 2010-SR.Quake-Sensitivity of Noninvasive Prenatal Detection of Fetal Aneuploidy from Maternal Plasma Using Shotgun Sequencing Is Limited Only by Counting Statistics
文中提到，这个公式是最重要的理论。
