The results of the DNA fingerprinting and amelogenin analysis confirmed the sex of three of the samples determined by array CGH and ruled out any sample mix up as the sampled fragments had a distinct set of STR alleles. In the fourth sample, only AMELX amplified from embryo 6, presumably as a result of ADO (Table 2). Furthermore, the absence of any paternal ETP-46464 and the presence of only a single maternal allele at each locus suggested that the DNA may have originated in a polar body with a haploid set of maternal chromosomes. Finally, genome-wide SNP genotyping and karyomapping identified beyond doubt that the DNA from the fragments was exclusively that of the second polar body corresponding to the embryo from which the trophectoderm cells had been sampled. The evidence for this is threefold: no paternal SNP markers were detected for any of the chromosomes; the grandparental origin of each of the 23 maternal chromosomes in both samples was identical (theoretically the chance of an identical set is 223:1); and, although most crossovers were in different positions, there were 12 crossovers in identical positions in both sets of maternal chromosomes consistent with distal crossovers between sister chromatids (Ottolini et al., 2015) (Figure 3). Furthermore, the maternal haplotypes identified by karyomapping at the STR loci are all concordant with the alleles detected by direct analysis (Table 2).