Patent ID: 8442774

Claim:
A method for performing prenatal diagnosis of a fetal chromosomal aneuploidy in a fetus by analyzing a biological sample obtained from a female subject pregnant with the fetus, wherein the biological sample includes nucleic acid molecules from the female subject and from the fetus, the method comprising: sequencing a plurality of the nucleic acid molecules contained in the biological sample to obtain paired-end sequence reads for each of the plurality of nucleic acid molecule; aligning the paired-end sequenced reads of the plurality of nucleic acid molecules to identify from which chromosomes the nucleic acid molecules originate; determining a length for each of the plurality of nucleic acid molecules based on the paired-end sequence reads; determining a first amount of nucleic acid molecules identified as originating from a first chromosome; determining a second amount of nucleic acid molecules identified as originating from one or more second chromosomes, wherein the determination of the first amount and the second amount is based on the determined lengths of the corresponding nucleic acid molecules; determining a parameter from the first amount and the second amount; comparing the parameter to one or more cutoff values; and based on the comparison, determining a classification of whether a fetal chromosomal aneuploidy exists for the first chromosome.