Chromosomal complement and clinical relevance of multinucleated embryos in PGD and PGS cycles

The objective of this retrospective study was to investigate the incidence and clinical implications of multinucleation in blastomeres biopsied from cleavage-stage embryos obtained from patients undergoing preimplantation genetic screening (PGS) for aneuploidies or preimplantation genetic diagnosis (PGD) for translocations or single-gene defects (SGD). A total of 3515 embryos were obtained from 306 couples in 380 PGD or PGS cycles. Incidence of multinucleation, chromosomal complement in multinucleated (MN) and sibling embryos and the characteristics of MN embryos resulting in healthy births were investigated. Of all cycles, 41.3% involved at least one MN embryo. There were more uniformly diploid than uniformly haploid nuclei (22.0% versus 7.9%, P<0.01). The most common form of abnormality was chaotic chromosomal complement (39.9%, 147/368). Transfer of embryos that had MN blastomeres free of the genetic abnormalities tested resulted in three healthy deliveries. It is concluded that, although the majority of MN blastomeres are chromosomally abnormal, healthy births are possible after transfer of embryos containing these blastomeres subjected to genetic analysis. As far as is known, this is the first report of healthy births after transfer of embryos with MN blastomeres tested for translocations or SGD in PGD cycles. Preimplantation genetic diagnosis (PGD) is an established method for selecting genetically healthy embryos for transfer. A blastomere sampled from the developing embryo is subjected to genetic analysis. Some of these blastomeres may contain multiple nuclei, complicating the genetic diagnosis. We investigated clinical implications of multinucleation in PGD cycles. Our results indicate that majority of the multinucleated blastomeres, and consequently embryos, are genetically abnormal. However, healthy births are possible after transfer of multinucleated embryos that are free of the genetic abnormalities screened.