Detecting fetal chromosomal abnormalities using tandem single nucleotide polymorphisms

1. A method for determining whether a fetus has an aneuploidy, said method comprising:

(a) providing a sample comprising maternal and fetal cell free DNA;

(b) designing primers directed to alleles of interest comprising tandem single nucleotide polymorphisms for specific chromosomal regions using computer software, wherein the alleles comprise tandem single nucleotide polymorphisms with single nucleotide polymorphisms that are at most 250 basepairs apart;

(c) enriching the sample for the alleles of interest using the designed primers to create isolated products;

(d) sequencing the isolated products;

(e) detecting isolated products from the chromosomal region of interests that comprise at least three different alleles, wherein each of the three different alleles of the chromosomal regions comprise different haplotypes of the tandem SNP;

(f) quantifying the detected isolated products to calculate a haplotype ratio for the alleles of interest at the chromosomal regions of interest;

(g) determining whether the fetus has an aneuploidy based on the calculated haplotype ratios.

2. The method of claim 1 , wherein the single nucleotide polymorphisms in the tandem single nucleotide polymorphism are at most 100 nucleotides apart.

3. The method of claim 2 , wherein the single nucleotide polymorphisms in the tandem single nucleotide polymorphism are at most 75 nucleotides apart.

4. The method of claim 3 , wherein the single nucleotide polymorphisms in the tandem single nucleotide polymorphism are at most 50 nucleotides apart.

5. The method of claim 1 , wherein the alleles of interest are enriched through amplification.

6. The method of claim 5 , wherein the primers are amplification primers used to enrich the alleles of interest.

7. The method of claim 1 , wherein the aneuploidy is a trisomy.

8. The method of claim 1 , wherein the aneuploidy is a monosomy.