Scoping review on the embryonic developmental potential of tripronuclear zygotes and their use for clinical and research purposes.

We reviewed the published literature on human 3PN zygotes, focusing on their developmental potential, genetic status, and possible correction, either spontaneous (autocorrection) or through micromanipulation. A total of 29 articles published between 2000 and 2023 were deemed eligible for this scoping review. Significant differences exist between the developmental potential of bipronucleated zygotes and 3PN zygotes, with the latter showing a lower blastulation rate and altered cleavage patterns, and this is related to the fertilization method used. 3PN embryos obtained by conventional IVF are most often diandric, and arrest their development more quickly with a lower blastulation rate, compared to those obtained by ICSI. This result may be linked to the number of centrioles establishing the first cytokinesis. Autocorrection can occur in 3PN zygotes, resulting in diploid embryos, and there have been reports of live births following the transfer of 3PN embryos. Induced diploidization through pronuclear removal by micromanipulation is technically feasible and associated with good survival rates. Because tripronuclear embryos are destined to be discarded, they can serve as a source of additional embryos for research purposes without major ethical concerns. Furthermore, the transfer of 3PN embryos, corrected either spontaneously or by micromanipulation, holds the potential to increase the pool of embryos eligible for transfer in IVF centers. However, this cannot be considered without genetic screening aiming to evaluate diploidy, euploidy, and heteroparental inheritance, and no studies have yet evaluated these three genetic aspects comprehensively. Further research is essential to fully understand the physiology and potential of corrected 3PN zygotes in the fields of assisted reproduction and research.