Method of detecting fetal chromosomal aneuploidy

A method of detecting chromosomal aneuploidy of a target fetal chromosome, the method comprising:

• obtaining sequence information (reads) of a plurality of nucleic acid fragments obtained from a biological sample of a pregnant woman;
• mapping the obtained reads to a reference human genome to assign the reads of the nucleic acid fragments to the chromosome;
• calculating a GC content and a fraction of reads (Rf) of the nucleic acid fragments on the target chromosome to the number of the nucleic acid fragments, based on the reads of the nucleic acid fragments assigned to the chromosome;
• selecting adaptive reference samples belonging to a shared range of unit values of Rf and unit values of GC content from reference samples, based on the calculated Rf and GC content on the target chromosome;
• calculating z scores of a verification reference samples and z scores of the test samples using the selected adaptive reference samples;
• and
• determining that the target chromosome has chromosomal aneuploidy when, by comparing the calculated z scores of the verification reference samples with the z scores of the test samples, the z scores of the test samples are larger than the z scores of the verification reference samples.