Prevalence and mechanistic origins of genome-wide ploidy abnormalities in ICSI derived human preimplantation embryos.

BACKGROUND: Genome-wide ploidy abnormalities (GWPA) constitute a distinct and clinically significant class of chromosomal errors that arise during human preimplantation development. However, the developmental origins and prevalence of GWPA remain incomplete and poorly understood. METHODS: To evaluate the frequency and origin of GWPA in human embryos, we have retrieved preimplantation genetic testing (PGT) haplotyping data, derived from 3798 blastomere and 3593 trophectoderm biopsies. Prior haplotype reconstruction and determination of parental origin were performed using B-allele frequency-aware haplotyping (haplarithmisis). RESULTS: GWPA were detected in 113 biopsies: 81 cleavage-stage embryos and 32 blastocysts. Genome-wide loss of heterozygosity of maternal origin was the most frequent abnormality. Triploidy was the second most common aberration present in 35 embryos: 24 cleavage-stage embryos and 11 blastocysts, with the majority resulting from maternal meiosis II errors. In addition, we uncover less-characterized abnormalities, providing new insights into the chromosomal mechanisms driving early human embryonic development. CONCLUSIONS: GWPA occur in 2.16% of cleavage-stage and 0.89% of blastocyst-stage ICSI embryos, showing a strong selection against GWPA during preimplantation development. This study also demonstrates that using appropriate methods to detect GWPA when screening ICSI embryos can help prevent the transfer of nonviable embryos.