Are tri-pronuclear embryos that show two normal-sized pronuclei and additional smaller pronuclei useful for embryo transfer?

PurposeThis study aimed to analyze whether tripronuclear (3PN) zygotes, with two normal-sized PNs and an additional smaller PN (2.1PN), can be used for embryo transfer.MethodsA retrospective embryo cohort study was conducted on 695 patients who underwent intracytoplasmic sperm injection treatment. Blastocyst formation rates were compared between 2.1PN and 2PN zygotes and PGT-A analysis was performed on 15 blastocysts derived from 2.1PN zygotes.ResultsBlastocyst formation rates were comparable between 2.1PN (43.8%) and 2PN zygotes (54.8%; p = 0.212). The rates of blastocysts with good morphology derived from 2.1 PN and 2PN zygotes were 18.8% and 25.5%, respectively. No significant differences were detected (p = 0.383). All of the analyzed blastocysts were diploid; however, 13 of these were found to be aneuploid, with a further two being mosaic.ConclusionOur results suggest that 2.1PN embryos can reach blastocyst stage. These blastocysts were diploid, however, predominantly aneuploid, and therefore could not be used for embryo transfer.