A method for providing a statistical likelihood of the presence or absence of fetal aneuploidy in a pregnant female with an egg donor pregnancy, comprising interrogating ten or more nucleic acid regions from a first chromosome from a maternal sample comprising maternal and fetal cell-free DNA, wherein the maternal sample is from the pregnant female; detecting the interrogated nucleic acid regions from the first chromosome; quantifying a relative frequency of alleles from the nucleic acid regions from the first chromosome; interrogating ten or more selected nucleic acid regions from a second chromosome; detecting the interrogated nucleic acid regions from the second chromosome; quantifying a relative frequency of alleles from the nucleic acid regions from the second chromosome; calculating a percent fetal cell-free DNA in the maternal sample using egg donor informative loci wherein the egg donor informative loci are nucleic acid reqions having the following allele patterns: the carrier mother is homozygous and the fetus is heterozygous; the carrier mother is heterozygous and the fetus is homozygous, or the carrier mother is homozygous for one allele and the fetus is homozygous for a different allele, wherein the egg donor informative loci are selected from the interrogated nucleic acid regions from the first and second chromosome; comparing the relative frequency of the nucleic acid regions from the first chromosome to the relative frequency of the nucleic acid regions from the second chromosome; and providing a statistical likelihood of the presence or absence of a fetal aneuploidy using the calculated percent fetal cell-free DNA in the maternal sample to determine the expected statistical presence of the fetal chromosomes. interrogating ten or more nucleic acid regions from a first chromosome from a maternal sample comprising maternal and fetal cell-free DNA, wherein the maternal sample is from the pregnant female; detecting the interrogated nucleic acid regions from the first chromosome; quantifying a relative frequency of alleles from the nucleic acid regions from the first chromosome; interrogating ten or more selected nucleic acid regions from a second chromosome; detecting the interrogated nucleic acid regions from the second chromosome; quantifying a relative frequency of alleles from the nucleic acid regions from the second chromosome; calculating a percent fetal cell-free DNA in the maternal sample using egg donor informative loci wherein the egg donor informative loci are nucleic acid reqions having the following allele patterns: the carrier mother is homozygous and the fetus is heterozygous; the carrier mother is heterozygous and the fetus is homozygous, or the carrier mother is homozygous for one allele and the fetus is homozygous for a different allele, wherein the egg donor informative loci are selected from the interrogated nucleic acid regions from the first and second chromosome; comparing the relative frequency of the nucleic acid regions from the first chromosome to the relative frequency of the nucleic acid regions from the second chromosome; and providing a statistical likelihood of the presence or absence of a fetal aneuploidy using the calculated percent fetal cell-free DNA in the maternal sample to determine the expected statistical presence of the fetal chromosomes. <EOS>