Uniparental disomy in the human blastocyst is exceedingly rare

ObjectiveTo establish whether uniparental disomy (UPD) could represent an outcome of embryonic aneuploidy self-correction and its relevance to preimplantation genetic diagnosis, and to validate a method of UPD detection in limited quantities of cells and determine the frequency of UPD in a large sample size of human blastocysts.DesignRetrospective observational.SettingAcademic center for reproductive medicine.Patient(s)Couples undergoing in vitro fertilization (IVF) treatment whose embryos underwent trophectoderm biopsy single-nucleotide polymorphism (SNP) array–based 24-chromosome aneuploidy screening.Intervention(s)None.Main Outcome Measure(s)Rate of UPD observed in the human blastocyst.Result(s)After application of defined thresholds, 2 of 3,401 blastocysts were found to possess isodisomy, and 0 were found to possess heterodisomy. The overall frequency of UPD in the human blastocyst was therefore 0.06%.Conclusion(s)This validated method of detection indicates that UPD is extremely rare and suggests that routine screening during preimplantation genetic diagnosis (PGD) may not be necessary. Furthermore, chromosomal UPD is unlikely to explain or support the existence of embryonic self-correction.