Molecular testing of multiple pregnancies

摘要

Methods, systems, and apparatus are provided for determining zygosity of a multiple-fetus pregnancy using a biological sample taken from the mother. The fetal and maternal DNA in the sample (e.g. plasma) can be analyzed for a particular chromosomal region to identify genetic differences in the fetuses. For example, a normalized parameter for the measure of a primary or secondary allele can show variances for different chromosomal regions when fetuses are dizygotic. Such a variance can be determined relative to an expected value if the fetuses were genetically identical. Statistical methods are provided for analyzing the variation of the normalized parameters to determine fetal DNA concentration and the maternal- fetal mixed genotype at various loci. Parental genotype and haplotype information can also be used to identify inheritance of different parental haplotypes to indicate genetic differences among the fetuses.