Patent Document ID: 20130178373
Application ID: 13791397
Patent Flag: 0

Claim One:
1. A method for determining a ploidy status of a chromosome or chromosome segment in a gestating fetus, the method comprising: measuring the DNA in a sample that comprises maternal DNA from the mother of the fetus and fetal DNA from the fetus at a plurality of polymorphic loci on the chromosome or chromosome segment; calculating, on a computer, allele counts at the plurality of polymorphic loci from the DNA measurements made on the sample; creating, on a computer, a plurality of ploidy hypotheses each pertaining to a different possible ploidy state of the chromosome or chromosome segment; building, on a computer, a joint distribution model for the expected allele counts at the plurality of polymorphic loci on the chromosome or chromosome segment for each ploidy hypothesis; determining, on a computer, a relative probability of each of the ploidy hypotheses using the joint distribution model and the allele counts measured on the sample; and calling the ploidy state of the fetus by selecting the ploidy state corresponding to the hypothesis with the greatest probability.