Validation of a targeted next generation sequencing-based comprehensive chromosome screening platform for detection of triploidy in human blastocysts.

Triploidy accounts for ~2% of natural pregnancies and 15% of cytogenetically abnormal miscarriages. This study aimed to validate triploidy detection in human blastocysts, its frequency and parental origin using genotyping data generated in parallel with chromosome copy number analysis by a targeted next generation sequencing (tNGS)-based comprehensive chromosome screening platform. Phase 1: diploid and triploid control samples were blinded, sequenced by tNGS and karyotype predictions compared for accuracy. Phase 2: tNGS was used to calculate the frequency of triploidy in 18,791 human blastocysts from trophectoderm (TE) biopsies. Phase 3: parental origin of the inherited extra alleles was evaluated by sequencing parental gDNA to validate triploidy predictions from Phase 2. All karyotypes and ploidy in controls from Phase 1 were correctly predicted by two independent methods. A blastocyst triploidy frequency of 0.474% (89/18,791) was observed in Phase 2 of the study. Finally, five suspected triploid blastocysts with parental DNA available were confirmed to be triploid and of maternal origin. tNGS provides higher sequencing depth in contrast to other contemporary NGS platforms, allowing for accurate single nucleotide polymorphism calling and accurate detection of triploidy in TE biopsies. Triploidy in intracytoplasmic sperm injection-derived blastocysts is rare and mostly of maternal origin.