Impact of multinucleated blastomeres on embryo developmental competence, morphokinetics, and aneuploidy.

OBJECTIVE: To study the effect of human embryo multinucleation on the rate of aneuploidy, in vitro developmental morphokinetics, and pregnancy outcome.

DESIGN: Retrospective study.

SETTING: University-affiliated fertility center.

PATIENT(S): A total of 296 patients undergoing IVF cycles.

INTERVENTION(S): None.

MAIN OUTCOME MEASURE(S): Rate of multinucleation at the 2- and 4-cell stage, time-lapse morphokinetic parameters from zygote to blastocyst stage, ploidy of embryos analyzed by means of trophectoderm biopsy and array comparative genomic hybridization (PGS), and pregnancy outcome.

RESULT(S): A total of 1,055 out of 2,441 (43.2%) embryos evaluated with the use of the Embryoscope time-lapse system showed blastomere multinucleation at the 2-cell stage (MN2). The frequency of this abnormality was substantially reduced in 4-cell-embryos (15.0%). Among all clinical factors analyzed, only maternal age had a positive correlation with multinucleation rate. The timing of cleavage divisions from the pronuclear fading to 5-cell embryo was significantly longer (1.0-2.5 h) in MN2 embryos than in non-MN2 control samples. Of the total embryos tested with the use of PGS (n = 607), the rates of multinucleation were similar in euploid versus aneuploid blastocysts (40.8% and 46.7%, respectively). All 24 chromosomes contributed to aneuploidy of MN2 embryos. There were 61 transfers of MN2 embryos that resulted in 45.9% clinical pregnancies and a 31.6% implantation rate.

CONCLUSION(S): The frequency of multinucleation is high in human embryos cultured in vitro and equally affects euploid and aneuploid human embryos. It appears that most MN embryos have the capacity for self-correction during early cleavage divisions and can develop into euploid blastocysts resulting in healthy babies.