SIZE-BASED ANALYSIS OF FETAL DNA FRACTION IN MATERNAL PLASMA

摘要

A maternal plasma sample of a pregnant woman is analysed. The sample includes cell-free DNA fragments originating from maternal cells and fetal cells. For each of a plurality of DNA fragments: one or more sequence reads is received, including both ends of the DNA fragment; the sequence reads are aligned to a reference genome to obtain aligned locations for both ends; and the aligned locations are used to determine a size of the DNA fragment. For each of a plurality of sizes, an amount of a set of the plurality of DNA fragments from the plasma sample corresponding to the size is determined. There is calculated a value of a first parameter based on the amounts of DNA fragments at multiple sizes, providing a statistical measure of a size profile of DNA fragments. The value is compared to a calibration value to estimate a fractional concentration of fetal DNA.